9. Dates and Times in Python (133m) Flashcards

Question 1

Q

what does dir(datetime) do in python?

Answer

A

In Python, the datetime module is part of the standard library and provides classes for manipulating dates and times. When you call dir(datetime), you are inspecting the attributes and methods of the datetime module.

Here’s an example of how to use dir(datetime):

```python
import datetime

print(dir(datetime))
~~~

When you run this code, it will display a list of attributes and methods available in the datetime module. The output will be a lengthy list, but here are some common attributes and methods you may find:

date: A class representing dates (datetime.date).
time: A class representing times (datetime.time).
datetime: A class representing both dates and times (datetime.datetime).
timedelta: A class representing the difference between two datetime values (datetime.timedelta).
timezone: A class representing time zones (datetime.timezone).
date.today(): A method that returns the current local date.
datetime.now(): A method that returns the current local date and time.
datetime.combine(): A method that combines a date object with a time object.
datetime.strptime(): A method that converts a string to a datetime object using a specified format.

These are just a few examples, and there are many more attributes and methods available in the datetime module. By using dir(datetime), you can explore the module’s functionality and discover all the available options for working with dates and times in Python.

Question 2

Q

In Python REPL, the following code is typed. What does it mean, explain it in detail:
~~~
import datetime
dir(datetime)

treehouse_start = datetime.datetime.now()
treehouse_start

treehouse_start = treehouse_start.replace(hour=4, minute=30, second=0, microsecond=0)
treehouse_start

time_worked = print(datetime.datetime.now() - treehouse_start)
time_worked
time_worked.seconds
time_worked.days
dir(time_worked)

hours_worked = round(time_worked.seconds/3600)
hours_worked
~~~

Answer

A

Certainly! Let’s go through the code step by step and provide the results for each line:

```python
import datetime
dir(datetime)
~~~
This imports the datetime module and then displays a list of names (attributes and methods) available in the datetime module. The output will be a long list of names specific to the datetime module.

```python
treehouse_start = datetime.datetime.now()
treehouse_start
~~~
This assigns the current date and time to the variable treehouse_start using the datetime.now() method. The datetime.now() method returns a datetime object representing the current local date and time. Printing treehouse_start will display the current date and time when it was assigned. For example:
~~~
2023-06-10 12:34:56.789012
~~~

```python
treehouse_start = treehouse_start.replace(hour=4, minute=30, second=0, microsecond=0)
treehouse_start
~~~
This modifies the treehouse_start variable by using the replace() method of the datetime object. It sets the hour to 4, the minute to 30, and sets the seconds and microseconds to 0. This effectively changes the time component of the treehouse_start variable. Printing treehouse_start will display the modified date and time. For example:
~~~
2023-06-10 04:30:00
~~~

```python
time_worked = print(datetime.datetime.now() - treehouse_start)
time_worked
~~~
This calculates the difference between the current date and time (datetime.datetime.now()) and the value stored in treehouse_start. The result is assigned to the time_worked variable. Additionally, the print() function is called to display the calculated time difference. The output of the print() statement will be the time difference between the two datetime objects. For example:
~~~
6:52:34.123456
~~~
However, since the print() function doesn’t return a value, the time_worked variable will be None.

```python
time_worked.seconds
~~~
This accesses the seconds attribute of the time_worked object. The seconds attribute represents the time difference in seconds. The output will be the number of seconds in the time difference. For example:
~~~
24754
~~~

```python
time_worked.days
~~~
This accesses the days attribute of the time_worked object. The days attribute represents the number of days in the time difference. The output will be the number of days in the time difference. For example:
~~~
0
~~~

```python
dir(time_worked)
~~~
This calls the dir() function on the time_worked object, displaying a list of names (attributes and methods) available in the time_worked object. The output will be a list of names specific to the time_worked object.

```python
hours_worked = round(time_worked.seconds/3600)
hours_worked
~~~
This calculates the number of hours worked by dividing the seconds attribute of time_worked by 3600 (the number of seconds in an hour). The result is rounded using the round() function and assigned to the hours_worked variable. Printing hours_worked will display the rounded number of hours worked. For example:
~~~
6
~~~

In summary, the code imports the datetime module, performs calculations to determine the time difference between two datetime objects, and calculates the number of hours worked.

Treehouse Notes:
Examples
~~~
»> import datetime
»> now = datetime.datetime.now()
»> morning = now.replace(hour=9, minute=0)
~~~
The above will make a variable now that represents now, and then change the time to 9 a.m. in the variable morning.

>>> datetime.datetime(2014, 10) - datetime.datetime(2014, 9)
The above will give back a datetime.timedelta object.

Question 3

Q

Challenge 4 Tasks:

Task 1: Import the datetime library.

Task 2: Create a variable named now that holds the results of datetime.datetime.now().

Task 3: Create a new variable called two that holds the value of now with the hour set to 14. Use the .replace() method.

Task 4: Finally, change two so its minute is 30.

Answer

A

Answer:

import datetime #1
now = datetime.datetime.now() #2
two = now.replace(hour=14) #3
two = two.replace(minute=30) #4

Question 4

Q

What does datetime.timedelta() do?

Answer

A

In Python, the datetime.timedelta() function is used to represent a duration or difference between two dates or times. It creates a timedelta object that encapsulates the duration in terms of days, seconds, microseconds, and milliseconds.

The syntax for creating a timedelta object using datetime.timedelta() is as follows:

```python
timedelta_object = datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)
~~~

You can specify various parameters to define the duration. Here’s a brief explanation of the parameters:

days: Represents the number of days in the duration.
seconds: Represents the number of seconds (and fraction of seconds) in the duration.
microseconds: Represents the number of microseconds in the duration.
milliseconds: Represents the number of milliseconds (1 millisecond = 1000 microseconds) in the duration.
minutes: Represents the number of minutes in the duration.
hours: Represents the number of hours in the duration.
weeks: Represents the number of weeks in the duration.

You can pass positive or negative values to these parameters to represent forward or backward durations in time.

Here are a few examples of creating timedelta objects using datetime.timedelta():

```python
import datetime

Create a timedelta representing 2 days
two_days = datetime.timedelta(days=2)

Create a timedelta representing 4 hours and 30 minutes
four_hours_thirty_minutes = datetime.timedelta(hours=4, minutes=30)

Create a timedelta representing 1 week and 3 days
one_week_three_days = datetime.timedelta(weeks=1, days=3)
~~~

The timedelta object allows you to perform various operations, such as addition, subtraction, comparison, and formatting, with other timedelta objects or datetime objects.

For example, you can add a timedelta to a datetime object to get a new datetime object representing a shifted time:

```python
import datetime

current_time = datetime.datetime.now()
shifted_time = current_time + datetime.timedelta(hours=2)
~~~

In this example, shifted_time will be the current time plus 2 hours.

timedelta objects are useful for performing calculations involving durations and differences between dates and times. They provide a flexible way to manipulate time intervals in Python.

TreamTreeHouse Notes:
timedelta objects represent gaps in time. They are returned when you subtract one datetime from another. They can also be assigned to a variable and then used to augment datetime objects.

Question 5

Q

In REPL of Python, the following codes are typed line by line, read and explain it each line by line in detail including what results each will give:

import datetime
now = datetime.datetime.now()
now
datetime.timedelta(hours=5)
datetime.timedelta(days=3)
now + datetime.timedelta(days=3)
now + datetime.timedelta(days=-5)
now - datetime.timedelta(days=5)
now.date()
now.time()
hour = datetime.timedelta(hours=1)
hour
workday = hour * 9
tomorrow = datetime.datetime.now().replace(hour=9, minute=0) + datetime.timedelta(days=1)
tomorrow
tomorrow + workday
appointment = datetime.timedelta(minutes=45)
appointment
start = datetime.datetime(2023, 7, 1, 12, 45)
start
end = start + appointment
end

Answer

A

Let’s go through the code line by line and explain the purpose and result of each line:

```python
import datetime
~~~
This line imports the datetime module from the Python standard library, which provides classes for working with dates and times.

```python
now = datetime.datetime.now()
now
~~~
This code creates a datetime object representing the current date and time using the now() method of the datetime class. The variable now stores this datetime object. Printing now will display the current date and time.

```python
datetime.timedelta(hours=5)
~~~
This line creates a timedelta object representing a duration of 5 hours. The output will be a timedelta object.

```python
datetime.timedelta(days=3)
~~~
This line creates a timedelta object representing a duration of 3 days. The output will be a timedelta object.

```python
now + datetime.timedelta(days=3)
~~~
This line performs an arithmetic operation by adding a timedelta object representing 3 days to the now datetime object. The result will be a new datetime object that is 3 days ahead of the current date and time.

```python
now + datetime.timedelta(days=-5)
~~~
This line subtracts a timedelta object representing 5 days from the now datetime object. The result will be a new datetime object that is 5 days in the past relative to the current date and time.

```python
now - datetime.timedelta(days=5)
~~~
This line performs another arithmetic operation by subtracting a timedelta object representing 5 days from the now datetime object. The result will be a new datetime object that is 5 days in the past relative to the current date and time.

```python
now.date()
~~~
This line extracts and returns the date portion of the now datetime object. The output will be a date object representing the current date.

```python
now.time()
~~~
This line extracts and returns the time portion of the now datetime object. The output will be a time object representing the current time.

```python
hour = datetime.timedelta(hours=1)
hour
~~~
This code creates a timedelta object representing a duration of 1 hour and assigns it to the variable hour. Printing hour will display the timedelta object.

```python
workday = hour * 9
workday
~~~
This code performs an arithmetic operation by multiplying the hour timedelta object by 9. The result will be a new timedelta object representing a workday of 9 hours.

```python
tomorrow = datetime.datetime.now().replace(hour=9, minute=0) + datetime.timedelta(days=1)
tomorrow
~~~
This code calculates a datetime object representing tomorrow’s date and sets the time to 9:00 AM. It first uses datetime.datetime.now() to get the current date and time, then calls replace() to change the time to 9:00 AM. Finally, it adds a timedelta object representing 1 day to get tomorrow’s date. Printing tomorrow will display the datetime object representing tomorrow at 9:00 AM.

```python
tomorrow + workday
~~~
This line performs an arithmetic operation by adding the workday timedelta object to the tomorrow datetime object. The result will be a new datetime object representing the date and time when the workday ends.

python
appointment = datetime.timedelta(minutes=45)
appointment

This line creates a timedelta object representing a duration of 45 minutes. The output will be a timedelta object.

```python
start = datetime.datetime(2023, 7, 1, 12, 45)
start
~~~
This line creates a datetime object representing a specific date and time: July 1, 2023, at 12:45 PM. The output will be a datetime object.

```python
end = start + appointment
end
~~~
This line performs an arithmetic operation by adding the appointment timedelta object to the start datetime object. The result will be a new datetime object representing the date and time when the appointment ends.

In summary, the code demonstrates various operations using the datetime module to work with dates, times, and durations. It showcases creating datetime and timedelta objects, performing arithmetic operations, and extracting date and time components.

Question 6

Q

what attributes is not availabe in timedelta?

Answer

A

The timedelta objects in Python do not have certain attributes. Here are the attributes that are not available in timedelta objects:

Years: timedelta objects do not have a direct attribute for years. This is because the duration represented by a year can vary depending on leap years and calendar specifics. To handle durations in terms of years, you would need to consider other methods or calculations.
Months: Similarly, timedelta objects do not have a direct attribute for months. As with years, the length of a month can vary, and there are considerations such as the number of days in the month and leap years.
Weeks: Although you can create a timedelta object with a parameter for weeks (datetime.timedelta(weeks=1)), the timedelta object itself does not have a dedicated attribute for weeks. However, you can access the equivalent duration in days using the days attribute and divide it by 7.
Total seconds: The timedelta object does not provide a direct attribute to obtain the total duration in seconds. However, you can calculate it manually by accessing the days, seconds, and microseconds attributes and converting them to seconds.

These limitations exist because timedelta objects primarily represent a duration in terms of days, seconds, and microseconds. The absence of attributes for years, months, weeks, and total seconds reflects the focus on a more precise representation of time intervals.

Question 7

Q

Challenge: Write a function called far_away that takes one argument, a timedelta. Add that timedelta to datetime.datetime.now() and return the resulting datetime object.

Answer

A

The answer is:

import datetime

def far_away(time):
    return datetime.datetime.now() + time

Explanation for the answer:

Certainly! Let’s go through the correct answer line by line and explain each line:

```python
import datetime
~~~
This line imports the datetime module from the Python standard library, which provides classes for working with dates and times.

```python
def far_away(time):
~~~
This line defines a function named far_away that takes one parameter called time. This parameter represents a timedelta object.

```python
return datetime.datetime.now() + time
~~~
This line calculates the current date and time using datetime.datetime.now() and adds the time timedelta object to it. The resulting datetime object is then returned by the function.

In summary, the far_away function takes a timedelta object as input and adds it to the current datetime using datetime.datetime.now(). The result is a new datetime object representing a future or past time relative to the current datetime, depending on the value of the timedelta.

The final code when running the above function with Print Statement:
Certainly! Here’s the modified code with a print statement added for the function and the code to run it:

```python
import datetime

def far_away(time):
return datetime.datetime.now() + time

delta = datetime.timedelta(days=5, hours=3, minutes=30)
result = far_away(delta)
print(result)
~~~

When you run this code, it will calculate the current datetime using datetime.datetime.now() and add the delta timedelta to it within the far_away function. The resulting datetime object is then assigned to the result variable.

Finally, the result datetime object is printed to the console using the print statement. It will display the current datetime plus the duration specified by the delta timedelta.

Please let me know if you have any further questions or if there’s anything else I can assist you with!

Question 8

Q

In Python, REPL the following codes are typed line by line, what output each code will give and explain it like you do to a beginner.

import datetime
now = datetime.datetime.now()
today = datetime.datetime.today()
now
today
today = datetime.datetime.combine(datetime.date.today(), datetime.time())
today
today.month
today.hour
today.year
now.hour
today.weekday()
now.timestamp()

Answer

A

Let’s go through each line of code and explain the output it will give:

import datetime
This line imports the datetime module, which provides classes for manipulating dates and times in Python.
now = datetime.datetime.now()
This line creates a variable now and assigns it the current date and time using the now() method of the datetime class. The output will be the current date and time in the format: YYYY-MM-DD HH:MM:SS.mmmmmm.
today = datetime.datetime.today()
This line creates another variable today and assigns it the current local date and time using the today() method of the datetime class. The output will be the same as the previous line, representing the current date and time.
now
When you type now and hit enter, it will simply display the value stored in the now variable, which is the current date and time. The output will be the same as in the second line.
today
Similar to the previous line, when you type today and hit enter, it will display the value stored in the today variable, which is the current local date and time. The output will be the same as in the third line.
today = datetime.datetime.combine(datetime.date.today(), datetime.time())
This line combines the current date, obtained from datetime.date.today(), with a default time value (midnight) to create a new datetime object. The output will be the current local date with a time of midnight (00:00:00).
today.month
By accessing the month attribute of the today variable, it will return the month component of the date stored in today. The output will be the current month as an integer, ranging from 1 to 12.
today.hour
By accessing the hour attribute of the today variable, it will return the hour component of the time stored in today. Since we set the time to midnight in the previous line, the output will be 0.
today.year
By accessing the year attribute of the today variable, it will return the year component of the date stored in today. The output will be the current year as a four-digit integer.
now.hour
By accessing the hour attribute of the now variable, it will return the hour component of the time stored in now. Since we obtained the current time in the second line, the output will be the current hour of the day as an integer.
today.weekday()
By calling the weekday() method on the today variable, it will return the day of the week as an integer, where Monday is 0 and Sunday is 6. The output will depend on the current day when you run the code.
now.timestamp()
By calling the timestamp() method on the now variable, it will return the timestamp value representing the current date and time. The output will be a floating-point number representing the number of seconds since January 1, 1970 (UNIX epoch time).

Question 9

Q

what does .timestamp() do?

Answer

A

The .timestamp() method is a built-in method provided by the datetime class in Python. It is used to obtain the timestamp value of a datetime object.

When you call the .timestamp() method on a datetime object, it returns a floating-point number representing the number of seconds since January 1, 1970, at 00:00:00 UTC (known as UNIX epoch time). The returned value represents the datetime object in UTC.

The .timestamp() method is particularly useful for converting datetime objects into a standardized format that can be easily compared, stored, or manipulated. It provides a consistent way to represent dates and times as numeric values.

Here’s an example to demonstrate the usage of the .timestamp() method:

```python
from datetime import datetime

Create a datetime object
datetime_obj = datetime(2023, 6, 1, 10, 30)

Get the timestamp value
timestamp = datetime_obj.timestamp()

print(timestamp)
~~~

In this example, we create a datetime object named datetime_obj, representing a specific date and time. By calling the .timestamp() method on datetime_obj, we obtain the timestamp value as a floating-point number.

The returned timestamp value represents the number of seconds since the UNIX epoch (January 1, 1970). This allows us to compare and perform arithmetic operations with other timestamps or perform conversions between different time representations.

Question 10

Q

Challenge: Write a function named minutes that takes two datetimes and, using timedelta.total_seconds() to get the number of seconds, returns the number of minutes, rounded, between them. The first will always be older and the second newer. You’ll need to subtract the first from the second.

Answer

A

Answer:

def minutes(datetime1, datetime2):
    duration = datetime2 - datetime1
    return round(duration.total_seconds()/60)

Explanation:
The provided answer includes the implementation of the minutes function that takes two datetime objects as arguments and calculates the number of minutes between them.

Here’s the explanation of the code:

The minutes function is defined, which takes two datetime objects as parameters: datetime1 (older datetime) and datetime2 (newer datetime).
We subtract datetime1 from datetime2 to obtain a timedelta object named duration. This represents the duration between the two datetime objects.
The total_seconds() method is called on the duration object to get the total number of seconds in the duration.
We divide the total seconds by 60 to convert it into minutes.
Finally, we use the round() function to round the result to the nearest whole number.
The rounded value is returned as the result of the function.

Here’s an example usage of the minutes function:

```python
from datetime import datetime

datetime1 = datetime.datetime(2023, 6, 1, 10, 30)
datetime2 = datetime.datetime(2023, 6, 1, 11, 15)

result = minutes(datetime1, datetime2)
print(result) # Output: 45
~~~

In this example, we have two datetime objects representing different times on the same day. We call the minutes function with datetime1 as the older datetime and datetime2 as the newer datetime. The function calculates the duration in minutes between the two datetimes and returns the rounded value, which is 45 in this case.

Now, let’s run the minutes function and print the result:

```python
datetime1 = datetime(2023, 6, 1, 10, 30)
datetime2 = datetime(2023, 6, 1, 11, 45)

result = minutes(datetime1, datetime2)
print(result) # Output: 75
~~~

In this example, we have updated datetime2 to be 15 minutes ahead of datetime1. When we run the minutes function with these updated values, it calculates the duration in minutes between the two datetimes, which is 75.

from datetime import datetime

def minutes(datetime1, datetime2):
    duration = datetime2 - datetime1
    return round(duration.total_seconds() / 60)

Example usage
datetime1 = datetime(2023, 6, 1, 10, 30)
datetime2 = datetime(2023, 6, 1, 11, 45)

result = minutes(datetime1, datetime2)
print(result)  # Output: 75

Question 11

Q

what does .strftime mean in python?

Answer

A

The .strftime() method is a built-in method in Python used to format a datetime object as a string. It stands for “string format time.”

When you call the .strftime() method on a datetime object, you provide a formatting string that specifies how you want the datetime to be represented as a string. The method then returns a formatted string representing the datetime object according to the specified format.

The formatting string can contain special directives that are replaced by corresponding date and time components. These directives begin with a percent sign (%) and are used to represent various parts of the datetime, such as year, month, day, hour, minute, and so on.

Here’s an example to illustrate the usage of the .strftime() method:

```python
from datetime import datetime

datetime_obj = datetime(2023, 6, 1, 10, 30)

formatted_string = datetime_obj.strftime(“%Y-%m-%d %H:%M:%S”)

print(formatted_string)
~~~

In this example, we have a datetime object named datetime_obj, representing a specific date and time. By calling the .strftime() method on datetime_obj and passing the formatting string "%Y-%m-%d %H:%M:%S", we format the datetime as a string in the format YYYY-MM-DD HH:MM:SS.

The returned formatted_string will be a string representing the datetime object in the specified format, in this case, something like "2023-06-01 10:30:00". The formatting directives %Y, %m, %d, %H, %M, and %S are replaced with the corresponding components of the datetime.

The .strftime() method is useful when you need to format and display a datetime object as a string in a customized format for various purposes, such as logging, file naming, or displaying dates and times to users in a specific format.

To display the month name in the desired format, you can use the %B directive in the formatting string when using the .strftime() method. The %B directive represents the full month name.

Here’s an example that demonstrates how to format a datetime object to display the month name:

```python
from datetime import datetime

datetime_obj = datetime(2023, 6, 1, 10, 30)

formatted_string = datetime_obj.strftime(“%B”)

print(formatted_string)
~~~

In this example, we have a datetime object named datetime_obj. By calling the .strftime() method on datetime_obj and passing the formatting string "%B", we extract the full month name.

The returned formatted_string will be a string representing the month name of the datetime object, in this case, "June". The %B directive is replaced with the full month name based on the datetime object.

If you want the month name in lowercase letters, you can use the %b directive instead of %B. The %b directive represents the abbreviated month name.

Here’s an example that demonstrates the usage of %b:

```python
from datetime import datetime

datetime_obj = datetime(2023, 6, 1, 10, 30)

formatted_string = datetime_obj.strftime(“%b”)

print(formatted_string)
~~~

In this example, the formatted_string will be "Jun", representing the abbreviated month name.

You can combine these directives with other formatting directives to achieve the desired format for displaying the month name within a larger formatted string.

Question 12

Q

Explain the following code:

import datetime
now = datetime.datetime.now()
now_string1 = now.strftime('%b - %d - %Y')
now_string2 = now.strftime('%d/%m/%Y')
print(now_string1)
print(now_string2)

Answer

A

Certainly! Let’s go through the provided code step by step and explain its functionality:

```python
import datetime
~~~
In this line, we import the datetime module, which provides classes for manipulating dates and times in Python.

```python
now = datetime.datetime.now()
~~~
Here, we call the now() method of the datetime class to obtain the current date and time. This creates a datetime object named now representing the current date and time.

```python
now_string1 = now.strftime(‘%b - %d - %Y’)
~~~
In this line, we use the .strftime() method on the now object to format it as a string. The %b directive represents the abbreviated month name, %d represents the day of the month, and %Y represents the four-digit year. These directives are combined with hyphens and spaces to create the desired format.

The formatted string is assigned to the variable now_string1, which will hold a string representing the current date and time in the format “Month - Day - Year”. For example, if the current date is June 1, 2023, the value of now_string1 will be something like “Jun - 01 - 2023”.

```python
now_string2 = now.strftime(‘%d/%m/%Y’)
~~~
Similarly, in this line, we use the .strftime() method to format the now object as a string. The %d directive represents the day of the month, %m represents the month as a two-digit number, and %Y represents the four-digit year. These directives are combined with slashes to create the desired format.

The formatted string is assigned to the variable now_string2, which will hold a string representing the current date and time in the format “Day/Month/Year”. For example, if the current date is June 1, 2023, the value of now_string2 will be something like “01/06/2023”.

```python
print(now_string1)
print(now_string2)
~~~
Finally, we print the values of now_string1 and now_string2 to the console. This will display the formatted strings representing the current date and time according to the specified formats.

For example, the output might be:
~~~
Jun - 01 - 2023
01/06/2023
~~~

The code demonstrates how to use the .strftime() method to format a datetime object as a string in different date and time formats.

Question 13

Q

What does strptime() do in Python?

Answer

A

The strptime() method is a built-in method in Python’s datetime module that is used to parse a string representing a date and time and convert it into a datetime object.

The name strptime() stands for “string parse time.” It takes two arguments: the string representing the date and time and the format string that specifies how the date and time are formatted in the string.

Here’s the general syntax of the strptime() method:

```python
datetime.datetime.strptime(date_string, format)
~~~

The date_string argument is the string representing the date and time that you want to parse, and the format argument is the formatting string that describes the structure of the date_string.

The format string uses various directives to represent the different parts of the date and time. These directives start with a percent sign (%) and are similar to the ones used in the strftime() method.

Here’s an example to illustrate the usage of the strptime() method:

```python
from datetime import datetime

date_string = ‘2023-06-01 10:30:00’
format_string = ‘%Y-%m-%d %H:%M:%S’

parsed_datetime = datetime.strptime(date_string, format_string)

print(parsed_datetime)
~~~

In this example, we have a date_string that represents a date and time in the format YYYY-MM-DD HH:MM:SS. We also have a format_string that matches the structure of the date_string.

By calling datetime.strptime(date_string, format_string), we parse the date_string using the specified format_string and obtain a datetime object called parsed_datetime. The strptime() method parses the string and creates a datetime object representing the date and time.

The parsed_datetime object can then be used to perform various operations with dates and times.

The strptime() method is particularly useful when you need to convert a string representing a date and time into a datetime object so that you can perform calculations, comparisons, or other operations using the rich functionality provided by the datetime module.

Treehouse Notes:
* strftime - Method to create a string from a datetime
* strptime - Method to create a datetime from a string according to a format string

Question 14

Q

Running in REPL, the following code:
~~~
import datetime
birthday = datetime.datetime.strptime(‘2023-06-11’, ‘%Y-%m-%d’)
birthday_party = datetime.datetime.strptime(‘2023-06-11 12:00’, ‘%Y-%m-%d %H:%M’)
birthday
birthday_party
~~~

Or running the same code as test.py with the following code:
~~~
import datetime
birthday = datetime.datetime.strptime(‘2023-06-11’, ‘%Y-%m-%d’)
birthday_party = datetime.datetime.strptime(‘2023-06-11 12:00’, ‘%Y-%m-%d %H:%M’)
print(birthday)
print(birthday_party)
~~~

Explain the code and the result.

Answer

A

The provided code imports the datetime module and uses the datetime.strptime() function to parse date strings and create datetime objects.

Here’s an explanation of the code and the expected results:

```python
import datetime
birthday = datetime.datetime.strptime(‘2023-06-11’, ‘%Y-%m-%d’)
birthday_party = datetime.datetime.strptime(‘2023-06-11 12:00’, ‘%Y-%m-%d %H:%M’)
birthday
birthday_party
~~~

In this code, the datetime module is imported, which provides classes for manipulating dates and times in Python.

The datetime.datetime.strptime() function is used to parse date strings and create datetime objects. It takes two arguments: the date string to parse and the format string that specifies the structure of the date string.

In the first line, '2023-06-11' is passed as the date string, and '%Y-%m-%d' is the format string. The format string %Y represents the four-digit year, %m represents the month as a two-digit number, and %d represents the day as a two-digit number. The strptime() function parses the date string and creates a datetime object representing the date '2023-06-11', which is assigned to the variable birthday.

In the second line, '2023-06-11 12:00' is passed as the date string, and '%Y-%m-%d %H:%M' is the format string. The format string includes the date format from the previous line ('%Y-%m-%d') and adds %H for the hour and %M for the minute. The strptime() function parses the date string and creates a datetime object representing the date and time '2023-06-11 12:00', which is assigned to the variable birthday_party.

The code then has two lines birthday and birthday_party without any print statements or other output operations. In a Python REPL environment, when you simply type the name of a variable and press Enter, it displays the value of that variable. So, when you run this code in a REPL, it will display the values of birthday and birthday_party without explicitly printing them.

For example, running the code in a Python REPL environment would display the following output:

datetime.datetime(2023, 6, 11, 0, 0)
datetime.datetime(2023, 6, 11, 12, 0)

The output shows the datetime objects birthday and birthday_party, representing the parsed dates and times, respectively. The values are displayed in the format datetime.datetime(year, month, day, hour, minute).

Question 15

Q

to_string(datetime_object) => “24 September 2012”

Challenge Task 1 of 2
Create a function named to_string that takes a datetime and gives back a string in the format “24 September 2012”.

timestrings.py:
~~~
## Examples
# from_string(“09/24/12 18:30”, “%m/%d/%y %H:%M”) => datetime
~~~

Create a new function named from_string that takes two arguments: a date as a string and an strftime-compatible format string, and returns a datetime created from them.

Answer

A

The answer is:

import datetime

def to_string(datetime1):
    date_to_string = datetime1.strftime('%d %B %Y')
    return date_to_string

def from_string(arg1, arg2):
    from_string = datetime.datetime.strptime(arg1, arg2)
    return from_string

date1 = datetime.datetime(2012, 9, 24)
date1_string = to_string(date1)
print(date1_string)

date_string = "09/24/12 18:30"
format_string = "%m/%d/%y %H:%M"
date_from_string = from_string(date_string, format_string)
print(date_from_string)

Certainly! Let’s go through the code step by step and explain its functionality:

```python
import datetime
~~~
This line imports the datetime module, which provides classes for manipulating dates and times in Python.

```python
def to_string(datetime1):
date_to_string = datetime1.strftime(‘%d %B %Y’)
return date_to_string
~~~
Here, we define the to_string function that takes a datetime object as a parameter, named datetime1. Inside the function, we use the strftime() method of the datetime object to format it as a string. The format string '%d %B %Y' specifies the structure of the desired string representation, with %d representing the day of the month, %B representing the full month name, and %Y representing the four-digit year. The formatted string is returned as the result of the function.

```python
def from_string(arg1, arg2):
from_string = datetime.datetime.strptime(arg1, arg2)
return from_string
~~~
In this part, we define the from_string function that takes two parameters: arg1 and arg2. arg1 represents the date string, and arg2 represents the format string. Inside the function, we use the strptime() method of the datetime class to parse the date string and create a datetime object. The strptime() method takes the date string and the format string as arguments and returns the corresponding datetime object.

```python
date1 = datetime.datetime(2012, 9, 24)
date1_string = to_string(date1)
print(date1_string)
~~~
In this section, we create a datetime object named date1 representing the date September 24, 2012. We then call the to_string function, passing date1 as an argument. The function formats date1 as a string using the %d %B %Y format, and the resulting string is assigned to the variable date1_string. Finally, we print the value of date1_string, which will be “24 September 2012”.

```python
date_string = “09/24/12 18:30”
format_string = “%m/%d/%y %H:%M”
date_from_string = from_string(date_string, format_string)
print(date_from_string)
~~~
In this part, we have a date string date_string representing “09/24/12 18:30”, and a format string format_string representing “%m/%d/%y %H:%M”. We call the from_string function, passing date_string and format_string as arguments. The function uses datetime.datetime.strptime() to parse the date string according to the format string and creates a datetime object representing the parsed date and time. The resulting datetime object is assigned to the variable date_from_string. Finally, we print the value of date_from_string, which will be the datetime object representing the parsed date and time.

By running the code, you will see the output:

24 September 2012
2012-09-24 18:30:00

The first line is the formatted string representing the datetime object date1, and the second line is the datetime object obtained from parsing the date_string using the specified format.

Question 16

Q

Challenge: Using python docs and strftime and strptime, make a script that accepts month and day date and returns to a link to wikipedia to that date.

Answer

A

Challenge: Using python docs and strftime and strptime, make a script that accepts month and day date and returns to a link to wikipedia to that date.

My answer:
~~~

import datetime
def open_wiki (month, day):
current_year = datetime.datetime.now().year
date_parsing = datetime.datetime.strptime(f’{current_year}-{month}-{day}’,’%Y-%m-%d’)
date_string_format = date_parsing.strftime(‘%B_%m’)
wiki_link = f’https://en.wikipedia.org/wiki/{date_string_format}’
return wiki_link

month = input(‘Enter the Month (MM): ‘)
day = input(‘Enter the Day (DD): ‘)
wiki = open_wiki(month, day)
print(wiki)
~~~

Teacher’s Answer:
~~~
import datetime
answer_format = ‘%m/%d’
link_format = ‘%B-%d’
link = ‘https://en.wikipedia.org/wiki/{}’

while True:
answer = input(“Please Enter the date in MM/DD format or Enter Quit to Quit: “)
if answer.upper() == ‘QUIT’:
break

try:
    date = datetime.datetime.strptime(answer, answer_format)
    output = link.format(date.strftime(link_format))
    print(output)
    
except ValueError():
    print("That's not a valid date. Please try again.") ~~~

Question 17

Q

Challenge: Write a function named time_tango that takes a date and a time. It should combine them into a datetime and return it.

Answer

A

My Answer:

import datetime

def time_tango(date, time):
    combined_datetime = datetime.datetime.combine(date, time)
    return combined_datetime

Question 18

Q

I want you to test the following code in REPL of Python, write down the steps to test the following code in REPL of Python:

class Question:
    answer = None
    text = None
    
class Add(Question):
    def \_\_init\_\_(self, num1, num2):
        self.text = '{} + {}'.format(num1, num2)
        self.answer = num1 + num2
        
class Multiply(Question):
    def \_\_init\_\_(self, num1, num2):
        self.text = '{} * {}'.format(num1, num2)
        self.answer = num1 * num2

Answer

A

Open REPL and then type the following:
~~~
from questions import Add
add1 = Add(3,5)
add1.text
add1.answer
~~~

add1.text will return ‘3+5’ and add1.answer will return ‘8’

Similarly you can test second class too:
~~~
from questions import Multiply
multiply1 = Multiply(3,5)
multiply1.text
multiply1.answer
~~~

multiply1.text will return ‘3 * 5’ and multiply1.answer will return ‘15’

Question 19

Q

Challenge: Write a function named delorean that takes an integer. Return a datetime that is that many hours ahead from starter.

import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

Answer

A

The answer is:

import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

def delorean(ahead):
    return starter.replace(hour=starter.hour+ahead)

Explanation:
Certainly! Let’s go through the corrected answer step by step:

```python
import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)
~~~

First, we import the datetime module and create a starter datetime object. In this case, the starter datetime represents October 21, 2015, at 16:29 (4:29 PM).

```python
def delorean(ahead):
return starter.replace(hour=starter.hour+ahead)
~~~

Next, we define the delorean function that takes an integer parameter called ahead. This parameter represents the number of hours we want to move ahead from the starter datetime.

The replace method of the datetime object is used here to create a new datetime object based on the starter datetime. By specifying the hour parameter as starter.hour+ahead, we can effectively move the hour component of the datetime forward by the desired number of hours.

For example, if we call delorean(3), the hour component of the starter datetime (which is 16) will be incremented by 3, resulting in a new datetime object with the hour component set to 19 (7 PM).

The function then returns this newly created datetime object.

Overall, this approach provides the correct answer by using the replace method to manipulate the hour component of the datetime object, effectively moving it forward by the specified number of hours.

Question 20

Q

Complete the following code:

Page 1: questions.py
~~~
class Question:
answer = None
text = None

class Add(Question):
def __init__(self, num1, num2):
self.text = ‘{} + {}’.format(num1, num2)
self.answer = num1 + num2

class Multiply(Question):
def __init__(self, num1, num2):
self.text = ‘{} * {}’.format(num1, num2)
self.answer = num1 * num2
~~~

Page 2: quiz.py
~~~
import datetime
import random

from questions import Add, Multiply

class Quiz:
questions = []
answers = []

def \_\_init\_\_(self):
    # generate 10 random questions with numbers from 1 to 10
    # add these questions into self.questions
    
def take_quiz(self):
    # log the start time
    # ask all of the questions
    # log if they got the question right
    # log the end time
    # show a summary
            
def ask(self, question):
    # log the start time
    # capture the answer
    # check the answer
    # log the end time
    # if the answer's right, send back True
    # otherwise, send back False
    # sendback the elapsed time too
    
def summary(self):
    # print how many you got right & the total # of questions. 5/10
    # print the total time for the quiz: 30 seconds! ~~~

Answer

A

Page 1: questions.py
```python
class Question:
answer = None
text = None

class Add(Question):
def __init__(self, num1, num2):
self.text = ‘{} + {}’.format(num1, num2)
self.answer = num1 + num2

class Multiply(Question):
def __init__(self, num1, num2):
self.text = ‘{} * {}’.format(num1, num2)
self.answer = num1 * num2
~~~

Page 2: quiz.py
```python
import datetime
import random

from questions import Add, Multiply

class Quiz:
questions = []
answers = []

def \_\_init\_\_(self):
    # generate 10 random questions with numbers from 1 to 10
    # add these questions into self.questions
    for _ in range(10):
        num1 = random.randint(1, 10)
        num2 = random.randint(1, 10)
        operation = random.choice([Add, Multiply])
        question = operation(num1, num2)
        self.questions.append(question)
    
def take_quiz(self):
    # log the start time
    start_time = datetime.datetime.now()
    
    # ask all of the questions
    for question in self.questions:
        if self.ask(question):
            self.answers.append(True)
        else:
            self.answers.append(False)
    
    # log the end time
    end_time = datetime.datetime.now()
    
    # show a summary
    self.summary(start_time, end_time)
            
def ask(self, question):
    # log the start time
    start_time = datetime.datetime.now()
    
    # capture the answer
    user_answer = input(question.text + ' = ')
    
    # check the answer
    if user_answer.isdigit() and int(user_answer) == question.answer:
        is_correct = True
    else:
        is_correct = False
    
    # log the end time
    end_time = datetime.datetime.now()
    
    # send back the elapsed time and if the answer is correct
    return is_correct, end_time - start_time
    
def summary(self, start_time, end_time):
    # print how many you got right & the total # of questions. 5/10
    correct_answers = sum(self.answers)
    total_questions = len(self.questions)
    print('You got {} out of {} questions right.'.format(correct_answers, total_questions))
    
    # print the total time for the quiz: 30 seconds!
    total_time = end_time - start_time
    print('Total time for the quiz: {} seconds!'.format(total_time.total_seconds())) ~~~

In the updated code, I have completed the implementation of the Quiz class and its methods:

In the \_\_init\_\_ method, 10 random questions are generated by choosing between addition and multiplication operations with random numbers between 1 and 10. Each question is then added to the self.questions list.
The take_quiz method logs the start time, asks all the questions one by one, and records whether the user’s answer is correct or not. The end time is logged after all the questions are asked.
The ask method handles asking an individual question. It logs the start time, captures the user’s answer, checks if the answer is correct, logs the end time, and returns a tuple containing the boolean value of whether the answer is correct and the elapsed time.
The summary method prints the number of questions answered correctly and the total number of questions. It also calculates and prints the total time taken for the quiz.

Now, you can create an instance of the `Quiz

` class and call the take_quiz method to run the quiz:

```python
quiz = Quiz()
quiz.take_quiz()
~~~

This will generate random questions and provide the user with an interactive quiz experience.

Page 1: questions.py
```python
class Question:
answer = None
text = None

class Add(Question):
def __init__(self, num1, num2):
self.text = ‘{} + {}’.format(num1, num2)
self.answer = num1 + num2

class Multiply(Question):
def __init__(self, num1, num2):
self.text = ‘{} * {}’.format(num1, num2)
self.answer = num1 * num2
~~~

Page 2: quiz.py
```python
import datetime
import random

from questions import Add, Multiply

class Quiz:
questions = []
answers = []

def \_\_init\_\_(self):
    # generate 10 random questions with numbers from 1 to 10
    # add these questions into self.questions
    for _ in range(10):
        num1 = random.randint(1, 10)
        num2 = random.randint(1, 10)
        operation = random.choice([Add, Multiply])
        question = operation(num1, num2)
        self.questions.append(question)
    
def take_quiz(self):
    # log the start time
    start_time = datetime.datetime.now()
    
    # ask all of the questions
    for question in self.questions:
        if self.ask(question):
            self.answers.append(True)
        else:
            self.answers.append(False)
    
    # log the end time
    end_time = datetime.datetime.now()
    
    # show a summary
    self.summary(start_time, end_time)
            
def ask(self, question):
    # log the start time
    start_time = datetime.datetime.now()
    
    # capture the answer
    user_answer = input(question.text + ' = ')
    
    # check the answer
    if user_answer.isdigit() and int(user_answer) == question.answer:
        is_correct = True
    else:
        is_correct = False
    
    # log the end time
    end_time = datetime.datetime.now()
    
    # send back the elapsed time and if the answer is correct
    return is_correct, end_time - start_time
    
def summary(self, start_time, end_time):
    # print how many you got right & the total # of questions. 5/10
    correct_answers = sum(self.answers)
    total_questions = len(self.questions)
    print('You got {} out of {} questions right.'.format(correct_answers, total_questions))
    
    # print the total time for the quiz: 30 seconds!
    total_time = end_time - start_time
    print('Total time for the quiz: {} seconds!'.format(total_time.total_seconds())) ~~~

In the updated code, I have completed the implementation of the Quiz class and its methods:

In the \_\_init\_\_ method, 10 random questions are generated by choosing between addition and multiplication operations with random numbers between 1 and 10. Each question is then added to the self.questions list.
The take_quiz method logs the start time, asks all the questions one by one, and records whether the user’s answer is correct or not. The end time is logged after all the questions are asked.
The ask method handles asking an individual question. It logs the start time, captures the user’s answer, checks if the answer is correct, logs the end time, and returns a tuple containing the boolean value of whether the answer is correct and the elapsed time.
The summary method prints the number of questions answered correctly and the total number of questions. It also calculates and prints the total time taken for the quiz.

Now, you can create an instance of the `Quiz

` class and call the take_quiz method to run the quiz:

```python
quiz = Quiz()
quiz.take_quiz()
~~~

This will generate random questions and provide the user with an interactive quiz experience.

Question 21

Q

Take up up the following code in Python IRL and test it and tell how would you test it. And explain the code written until now.

import datetime
import random

from questions import Add, Multiply

class Quiz:
    questions = []
    answers = []

    def \_\_init\_\_(self):
        question_types = (Add, Multiply)
        # generate 10 random questions with numbers from 1 to 10
        for _ in range(10):
            num1 = random.randint(1, 10)
            num2 = random.randint(1, 10)
            question = random.choice(question_types)(num1, num2)
            # add these questions into self.questions
            self.questions.append(question)

    def take_quiz(self):
        # log the start time
        # ask all of the questions
        # log if they got the question right
        # log the end time
        # show a summary
        pass

    def ask(self, question):
        # log the start time
        # capture the answer
        # check the answer
        # log the end time
        # if the answer's right, send back True
        # otherwise, send back False
        # send back the elapsed time, too
        pass

    def total_correct(self):
        # return the total # of correct answers
        total = 0
        for answer in self.answers:
            if answer[0]:
                total += 1
        return total

    def summary(self):
        # print how many you got right and the total # of questions. 5/10
        print('You got {} right out of {}'.format(self.total_correct(), len(self.questions)))
        # print the total time for the quiz: 30 seconds!
        print('It took you {} seconds total.'.format((self.end_time - self.start_time).seconds))

Answer

A

To test the code in Python IRL, open Python IRL and type the following:

from quiz import Quiz
quiz1 = Quiz
quiz1.answers
quiz1.questions
quiz1.questions[0].text
quiz.questions[0].answer

In the above, quiz1.answers will return empty string [] and quiz1.questions will return list of questions, and quiz1.questions[0].text will return a text of question like ‘4x10’ and finally quiz.questions[0].answer will return answer for the question ‘40’.

Explanation:
The provided code defines a class called Quiz that represents a quiz game. Let’s go through each part of the code and understand its functionality:

The code imports the necessary modules, datetime and random, which are used for working with dates/times and generating random numbers, respectively. It also imports two classes, Add and Multiply, from a module called questions. These classes likely represent question types for the quiz.
The Quiz class is defined with two class-level variables: questions and answers. These variables are used to store the questions and user answers for the quiz.
The \_\_init\_\_ method is the constructor of the Quiz class. It initializes a new instance of the class and populates the questions list with 10 random questions. It does this by iterating 10 times and generating two random numbers between 1 and 10. It then creates a question object by randomly choosing one of the question types (Add or Multiply) and passing the random numbers as arguments. The created question is added to the questions list.
The take_quiz method is a placeholder method that is currently empty. It is intended to handle the process of taking the quiz. This includes logging the start time, asking the questions, logging if the user got each question right, logging the end time, and showing a summary of the quiz. This method needs to be implemented with the necessary logic to perform these actions.
The ask method is another placeholder method. It takes a question object as an argument and is responsible for handling the process of asking a single question. This includes logging the start time, capturing the user’s answer, checking if the answer is correct, logging the end time, and returning the result (True if the answer is correct, False otherwise) along with the elapsed time. This method also needs to be implemented with the appropriate logic.
The total_correct method calculates and returns the total number of correct answers. It iterates over the answers list and checks if the first element of each answer tuple (which represents if the answer is correct or not) is True. If it is True, it increments the total variable. Finally, it returns the total value.
The summary method is responsible for printing a summary of the quiz. It displays the number of questions the user got right out of the total number of questions and the total time taken for the quiz. It uses the total_correct method to get the number of correct answers and calculates the total time by subtracting the end_time from the start_time. The summary is printed using formatted strings.

Note that there are pass statements in the take_quiz and ask methods, which are simply placeholders indicating that the methods are empty and need to be implemented with the required logic.

Overall, the provided code sets up the structure for a quiz game but requires further implementation to handle the actual quiz-taking process and display the results.

Question 22

Q

Challenge: Write a function named time_machine that takes an integer and a string of “minutes”, “hours”, “days”, or “years”. This describes a timedelta. Return a datetime that is the timedelta’s duration from the starter datetime.

time_machine.py:
~~~
import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

Remember, you can’t set “years” on a timedelta!
# Consider a year to be 365 days.

Example
# time_machine(5, “minutes”) => datetime(2015, 10, 21, 16, 34)
~~~

Answer

A

There is two ways to solve this:

Solution 1:
~~~
import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

def time_machine(integer, string):
if string == ‘years’:
string = ‘days’
integer *= 365
return starter + datetime.timedelta(**{string: integer})

result = time_machine(5, ‘days’)
print(result)
~~~

Explanation for Solution 1:
Certainly! Here’s a more detailed explanation of the code:

The code imports the datetime module, which provides classes for working with dates and times.
The code initializes a starter datetime object using the datetime.datetime class. The datetime.datetime constructor takes arguments representing the year, month, day, hour, minute, and second to create a specific datetime. In this case, the starter datetime is set to October 21, 2015, 16:29 (4:29 PM).
The time_machine function is defined, which takes two parameters: integer and string.
Inside the function, there is an if statement that checks if the value of the string parameter is equal to the string 'years'. This condition checks if the specified duration is in years.
If the condition is true, the code inside the if block is executed. This block changes the unit of time from years to days. It reassigns the value of the string parameter to the string 'days', indicating that the duration will now be interpreted as days. Additionally, the integer parameter is multiplied by 365 to convert the duration from years to the equivalent number of days.
The function then creates a timedelta object using the datetime.timedelta class. The timedelta class represents a duration or difference between two datetime objects. It takes keyword arguments to specify the duration in terms of different units of time. In this case, the **{string: integer} syntax is used to pass the values of string and integer as keyword arguments to the timedelta constructor. This allows the function to specify the duration in the desired unit of time (either ‘days’ or ‘years’) and the corresponding integer value.
The resulting timedelta object represents the specified duration. The function then adds this timedelta to the starter datetime object using the + operator.
The function returns the resulting datetime, which is the starter datetime plus the specified duration.
After defining the function, the code calls the time_machine function with arguments 5 and 'days'. This means that the desired duration is 5 days. The function calculates the resulting datetime by adding 5 days to the starter datetime.
Finally, the code prints the resulting datetime, which represents the starter datetime plus a timedelta of 5 days. The output will be the resulting datetime object.

In summary, the code provides a function time_machine that allows you to calculate a new datetime by adding a specified duration to a fixed starting datetime. It supports durations in either days or years. The function performs the necessary conversions and uses the datetime.timedelta class to represent the duration and perform the datetime calculations.

Solution 2:
~~~
import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

def time_machine(duration, unit):
if unit == “minutes”:
delta = datetime.timedelta(minutes=duration)
elif unit == “hours”:
delta = datetime.timedelta(hours=duration)
elif unit == “days”:
delta = datetime.timedelta(days=duration)
elif unit == “years”:
delta = datetime.timedelta(days=365 * duration)
else:
raise ValueError(“Invalid unit specified.”)

return starter + delta

result = time_machine(5, “minutes”)
print(result)
~~~

Explanation for Solution 2:
The provided code performs datetime calculations using the datetime module. Let’s break it down step by step:

The code imports the datetime module, which provides classes for working with dates and times.
The code initializes a starter datetime object using the datetime.datetime class. The datetime.datetime constructor takes arguments representing the year, month, day, hour, minute, and second to create a specific datetime. In this case, the starter datetime is set to October 21, 2015, 16:29 (4:29 PM).
The time_machine function is defined, which takes two parameters: duration and unit.
Inside the function, there is an if statement that checks the value of the unit parameter to determine the desired unit of time.
If unit is equal to the string "minutes", the code inside the corresponding if block is executed. It creates a timedelta object using the datetime.timedelta class with the minutes keyword argument set to the value of duration. This creates a duration of duration minutes.
If unit is equal to the string "hours", the code inside the corresponding elif block is executed. It creates a timedelta object with the hours keyword argument set to the value of duration. This creates a duration of duration hours.
If unit is equal to the string "days", the code inside the corresponding elif block is executed. It creates a timedelta object with the days keyword argument set to the value of duration. This creates a duration of duration days.
If unit is equal to the string "years", the code inside the corresponding elif block is executed. It calculates the number of days in duration years by multiplying 365 by the value of duration. It then creates a timedelta object with the days keyword argument set to this calculated value. This creates a duration of approximately duration years.
If none of the above conditions are met, the else block is executed. It raises a ValueError with the message "Invalid unit specified.". This ensures that the code handles cases where an unsupported unit is passed to the function.
The function returns the resulting datetime by adding the timedelta object to the starter datetime. The + operator is used to perform the addition.
After defining the function, the code calls the time_machine function with arguments 5 and "minutes". This means that the desired duration is 5 minutes. The function calculates the resulting datetime by adding 5 minutes to the starter datetime.
Finally, the code prints the resulting datetime, which represents the starter datetime plus a timedelta of 5 minutes. The output will be the resulting datetime object.

In summary, the code demonstrates how to use the time_machine function to calculate a new datetime by adding a specified duration in various units of time (minutes, hours, days, or years) to a fixed starting datetime (starter). The code performs the necessary calculations using the datetime.timedelta class to create timedelta objects representing durations and uses the + operator to add them to the starter datetime.

Question 23

Q

The following Quiz challenge app code base is:

questions.py:
~~~
class Question:
answer = None
text = None

class Add(Question):
def __init__(self, num1, num2):
self.text = ‘{} + {}’.format(num1, num2)
self.answer = num1 + num2

class Multiply(Question):
def __init__(self, num1, num2):
self.text = ‘{} x {}’.format(num1, num2)
self.answer = num1 * num2
~~~

quiz.py:
~~~
import datetime
import random

from questions import Add, Multiply

class Quiz:
questions = []
answers = []

def \_\_init\_\_(self):
    question_types = (Add, Multiply)
    # generate 10 random questions with numbers from 1 to 10
    for _ in range(10):
        num1 = random.randint(1, 10)
        num2 = random.randint(1, 10)
        question = random.choice(question_types)(num1, num2)
        # add these questions into self.questions
        self.questions.append(question)

def take_quiz(self):
    # log the start time
    self.start_time = datetime.datetime.now()
    # ask all of the questions
    for question in self.questions:
        # log if they got the question right
        self.answers.append(self.ask(question))
    else:
        # log the end time
        self.end_time = datetime.datetime.now()
    # show a summary
    return self.summary()

def ask(self, question):
    correct = False
    # log the start time
    question_start = datetime.datetime.now()
    # capture the answer
    answer = input(question.text + ' = ')
    # check the answer
    if answer == str(question.answer):
        correct = True
    # log the end time
    question_end = datetime.datetime.now()
    # if the answer's right, send back True
    # otherwise, send back False
    # send back the elapsed time, too
    return correct, question_end - question_start

def total_correct(self):
    # return the total # of correct answers
    total = 0
    for answer in self.answers:
        if answer[0]:
            total += 1
    return total

def summary(self):
    # print how many you got right and the total # of questions. 5/10
    print('You got {} right out of {}'.format(self.total_correct(), len(self.questions)))
    # print the total time for the quiz: 30 seconds!
    print('It took you {} seconds total.'.format((self.end_time - self.start_time).seconds))

Quiz().take_quiz()
~~~

Explain the code-base in detail.

Answer

A

The provided code consists of two files: questions.py and quiz.py. Let’s explain each file in detail:

questions.py:

This file defines two classes, Question and its subclasses Add and Multiply. Here’s a breakdown of the code:

Question class:
- This is the base class for all questions.
- It has two attributes: answer and text.
- answer is initialized to None and represents the correct answer to the question.
- text is initialized to None and represents the text of the question.
Add class (subclass of Question):
- This class represents an addition question.
- It inherits from the Question class and overrides its constructor (\_\_init\_\_ method).
- The constructor takes two parameters, num1 and num2, which are the numbers to be added.
- Inside the constructor, the text attribute is set to a string that represents the question, using the num1 and num2 values.
- The answer attribute is set to the sum of num1 and num2.
Multiply class (subclass of Question):
- This class represents a multiplication question.
- It also inherits from the Question class and overrides its constructor.
- The constructor takes two parameters, num1 and num2, which are the numbers to be multiplied.
- Inside the constructor, the text attribute is set to a string that represents the question, using the num1 and num2 values.
- The answer attribute is set to the product of num1 and num2.

quiz.py:

This file defines a class Quiz that represents a quiz. It uses the classes defined in questions.py to generate random math questions. Here’s a breakdown of the code:

Import statements:
- The datetime module is imported to work with dates and times.
- The random module is imported to generate random numbers.
Quiz class:
- This class represents a quiz.
- It has two class-level attributes: questions and answers.
- questions is initialized as an empty list to store the generated questions.
- answers is initialized as an empty list to store the user’s answers.
\_\_init\_\_ method:
- This method is the constructor of the Quiz class.
- It generates 10 random questions by iterating over a range of 10.
- For each iteration, it generates two random numbers between 1 and 10 using random.randint.
- It selects a random question type (either Add or Multiply) from the question_types tuple.
- It creates an instance of the selected question type and passes the generated numbers as arguments.
- The generated question is appended to the questions list.
take_quiz method:
- This method starts the quiz.
- It logs the start time using datetime.datetime.now() and assigns it to the start_time attribute.
- It iterates over each question in the questions list.
- For each question, it asks the user for an answer using the input function and stores it in the answer variable.
- It checks if the user’s answer matches the correct answer of the question. If it does, it sets correct to True.
- It logs the end time using datetime.datetime.now() and assigns it to the `

question_endvariable. - It returns a tuple containingcorrect and the time taken to answer the question (the difference between question_end and question_start). - The tuple is appended to theanswerslist. - After answering all the questions, it logs the end time of the quiz in theend_timeattribute. - It returns the result of calling thesummary` method.

ask method:
- This method takes a question parameter and handles asking a single question.
- It logs the start time of the question and assigns it to the question_start variable.
- It uses the input function to prompt the user with the text of the question and stores their answer in the answer variable.
- It checks if the user’s answer is equal to the correct answer of the question. If it matches, it sets correct to True.
- It logs the end time of the question and assigns it to the question_end variable.
- It returns a tuple containing correct and the time taken to answer the question (the difference between question_end and question_start).
total_correct method:
- This method calculates and returns the total number of correct answers.
- It iterates over the answers list and increments a counter (total) for each correct answer.
- It returns the value of the total counter.
summary method:
- This method prints a summary of the quiz.
- It prints the number of correct answers and the total number of questions.
- It calculates and prints the total time taken for the quiz (the difference between end_time and start_time).
Quiz execution:
- An instance of the Quiz class is created (Quiz()).
- The take_quiz method is called on the instance, which starts the quiz and returns the result of the summary method.
- The result is printed to the console.

In summary, the code defines a quiz app that generates random math questions and allows the user to answer them. It tracks the user’s answers, calculates the number of correct answers, and provides a summary of the quiz with the total correct answers and the time taken to complete it.

Question 24

Q

The following Quiz challenge app code base is:

questions.py:
~~~
class Question:
answer = None
text = None

class Add(Question):
def __init__(self, num1, num2):
self.text = ‘{} + {}’.format(num1, num2)
self.answer = num1 + num2

class Multiply(Question):
def __init__(self, num1, num2):
self.text = ‘{} x {}’.format(num1, num2)
self.answer = num1 * num2
~~~

quiz.py:
~~~
import datetime
import random

from questions import Add, Multiply

class Quiz:
questions = []
answers = []

def \_\_init\_\_(self):
    question_types = (Add, Multiply)
    # generate 10 random questions with numbers from 1 to 10
    for _ in range(10):
        num1 = random.randint(1, 10)
        num2 = random.randint(1, 10)
        question = random.choice(question_types)(num1, num2)
        # add these questions into self.questions
        self.questions.append(question)

def take_quiz(self):
    # log the start time
    self.start_time = datetime.datetime.now()
    # ask all of the questions
    for question in self.questions:
        # log if they got the question right
        self.answers.append(self.ask(question))
    else:
        # log the end time
        self.end_time = datetime.datetime.now()
    # show a summary
    return self.summary()

def ask(self, question):
    correct = False
    # log the start time
    question_start = datetime.datetime.now()
    # capture the answer
    answer = input(question.text + ' = ')
    # check the answer
    if answer == str(question.answer):
        correct = True
    # log the end time
    question_end = datetime.datetime.now()
    # if the answer's right, send back True
    # otherwise, send back False
    # send back the elapsed time, too
    return correct, question_end - question_start

def total_correct(self):
    # return the total # of correct answers
    total = 0
    for answer in self.answers:
        if answer[0]:
            total += 1
    return total

def summary(self):
    # print how many you got right and the total # of questions. 5/10
    print('You got {} right out of {}'.format(self.total_correct(), len(self.questions)))
    # print the total time for the quiz: 30 seconds!
    print('It took you {} seconds total.'.format((self.end_time - self.start_time).seconds))

Quiz().take_quiz()
~~~

Do the following challenge and explain it step by step:
1. Change the app so it takes a number of questions to generate.
2. Make sure the user can specify the range they want the numbers to come from.
3. Add in some further stats that tell you how long it took to answer each question.

And finally run it.

Answer

A

To implement the requested changes and enhancements, we need to modify the Quiz class in quiz.py. Here’s the modified code with step-by-step explanations:

```python
import datetime
import random

from questions import Add, Multiply

class Quiz:
questions = []
answers = []

def \_\_init\_\_(self, num_questions, range_min, range_max):
    question_types = (Add, Multiply)
    # generate random questions based on user-specified inputs
    for _ in range(num_questions):
        num1 = random.randint(range_min, range_max)
        num2 = random.randint(range_min, range_max)
        question = random.choice(question_types)(num1, num2)
        self.questions.append(question)

def take_quiz(self):
    # log the start time
    self.start_time = datetime.datetime.now()
    # ask all of the questions
    for question in self.questions:
        # log if they got the question right and the time taken
        self.answers.append(self.ask(question))
    else:
        # log the end time
        self.end_time = datetime.datetime.now()
    # show a summary
    return self.summary()

def ask(self, question):
    correct = False
    # log the start time
    question_start = datetime.datetime.now()
    # capture the answer
    answer = input(question.text + ' = ')
    # check the answer
    if answer == str(question.answer):
        correct = True
    # log the end time
    question_end = datetime.datetime.now()
    # send back whether the answer is correct, elapsed time, and the question
    return correct, question_end - question_start, question

def total_correct(self):
    # return the total # of correct answers
    total = 0
    for answer in self.answers:
        if answer[0]:
            total += 1
    return total

def summary(self):
    # print how many you got right and the total # of questions: 5/10
    print('You got {} right out of {}'.format(self.total_correct(), len(self.questions)))
    # print the total time for the quiz: 30 seconds!
    print('It took you {} seconds total.'.format((self.end_time - self.start_time).seconds))
    # print time taken for each question
    for answer in self.answers:
        question = answer[2]
        time_taken = answer[1].seconds
        print('Time taken for "{}" question: {} seconds'.format(question.text, time_taken))

num_questions = int(input(“Enter the number of questions to generate: “))
range_min = int(input(“Enter the minimum range for numbers: “))
range_max = int(input(“Enter the maximum range for numbers: “))

Quiz(num_questions, range_min, range_max).take_quiz()
~~~

Now let’s break down the changes and enhancements step by step:

Taking a number of questions to generate:
- We modify the \_\_init\_\_ method of the Quiz class to accept a new parameter num_questions.
- The user specifies the number of questions they want to generate as an input.
- Instead of generating a fixed number of 10 questions, we generate the number of questions based on the user’s input using a for loop.
Allowing the user to specify the range of numbers:
- We introduce two new parameters, range_min and range_max, in the \_\_init\_\_ method of the Quiz class.
- The user provides the minimum and maximum range for the random numbers to be used in the questions as inputs.
- The num1 and num2 values for each question

are generated using random.randint(range_min, range_max).

Additional statistics for each question:
- We modify the ask method to include the question itself in the return value, along with whether the answer is correct and the elapsed time.
- Inside the take_quiz method, after asking all the questions, we iterate over the answers and print the time taken for each question using the additional statistics.

Finally, the modified code prompts the user to enter the number of questions to generate, as well as the range for the random numbers. The Quiz class is instantiated with the user-provided inputs, and the take_quiz method is called to start the quiz. The summary and additional statistics are then printed.

By running this code, you can generate a customized quiz with a specified number of questions and range of numbers. The app will track the user’s answers, provide a summary of the quiz, and display the time taken for each question.

Question 25

Q

Challenge: Create a function named timestamp_oldest that takes any number of POSIX timestamp arguments. Return the oldest one as a datetime object.

Remember, POSIX timestamps are floats and lists have a .sort() method.

# If you need help, look up datetime.datetime.fromtimestamp()
# Also, remember that you *will not* know how many timestamps
# are coming in.

Answer

A

Solution 1:

import datetime

def timestamp_oldest(*args):
    return datetime.datetime.fromtimestamp(min(args))

Prompt the user to enter POSIX timestamps
timestamps_input = input("Enter the POSIX timestamps (separated by spaces): ")
timestamps = [float(timestamp) for timestamp in timestamps_input.split()]

Call the timestamp_oldest function with the provided timestamps
oldest_datetime = timestamp_oldest(*timestamps)

Print the oldest datetime
print("The oldest timestamp is:", oldest_datetime)

Solution 2:
~~~
import datetime

def timestamp_oldest(*timestamps):
sorted_timestamps = sorted(timestamps)
oldest_timestamp = sorted_timestamps[0]
return datetime.datetime.fromtimestamp(oldest_timestamp)

Example usage
timestamps = [1625167440.0, 1625171460.0, 1625153520.0]
oldest_datetime = timestamp_oldest(*timestamps)
print(oldest_datetime)
~~~

Question 26

Q

The following code is run in Python REPL, explain the following codes:

import datetime
pacific = datetime.timezone(datetime.timedelta(hours=-8))
eastern = datetime.timezone(datetime.timedelta(hours=-5))
mumbai = datetime.timezone(datetime.timedelta(hours=5, minutes=30))
naive = datetime.datetime(2014, 4, 21, 9)
aware = datetime.datetime(2014, 4, 21, 9, tzinfo=pacific)
aware.astimezone(eastern)
aware.astimezone(mumbai)

Answer

A

Certainly! Let’s dive into a more detailed explanation of the code:

import datetime: This line imports the datetime module, which is a part of Python’s standard library and provides classes for working with dates, times, and time zones.
pacific = datetime.timezone(datetime.timedelta(hours=-8)): Here, we create a timezone object named pacific representing the Pacific time zone. The timezone class is instantiated with a timedelta object specifying a time offset of -8 hours from UTC (Coordinated Universal Time). In other words, it represents a time zone that is 8 hours behind UTC.
eastern = datetime.timezone(datetime.timedelta(hours=-5)): This line creates a timezone object named eastern representing the Eastern time zone. It is similar to the previous line, but the time offset is -5 hours from UTC, indicating that this time zone is 5 hours behind UTC.
mumbai = datetime.timezone(datetime.timedelta(hours=5, minutes=30)): This line creates a timezone object named mumbai representing the Mumbai time zone. It uses the timezone class and specifies a time offset of 5 hours and 30 minutes ahead of UTC, indicating that this time zone is 5 hours and 30 minutes ahead of UTC.
naive = datetime.datetime(2014, 4, 21, 9): Here, we create a datetime object named naive representing a specific date and time. It specifies the date as April 21, 2014, and the time as 9:00 AM. However, this datetime object doesn’t have any time zone information associated with it, so it’s considered “naive.”
aware = datetime.datetime(2014, 4, 21, 9, tzinfo=pacific): This line creates a datetime object named aware representing a specific date and time in the Pacific time zone. It is similar to the previous line, but it includes the tzinfo argument, which is set to the pacific time zone object. This makes the aware object “aware” of its time zone, meaning it has time zone information associated with it.
aware.astimezone(eastern): This line converts the aware datetime object from the Pacific time zone to the Eastern time zone. The astimezone() method is called on the aware object, passing the eastern time zone object as an argument. This method performs the necessary calculations to adjust the time to the equivalent in the Eastern time zone. The result of this line is a new datetime object representing the same moment in time but expressed in the Eastern time zone.
aware.astimezone(mumbai): Similarly to the previous line, this line converts the aware datetime object from the Pacific time zone to the Mumbai time zone. The astimezone() method is called on the aware object, passing the mumbai time zone object as an argument. The method performs the necessary calculations to adjust the time to the equivalent in the Mumbai time zone. The result is a new datetime object representing the same moment in time but expressed in the Mumbai time zone.

In summary, the code showcases the usage of the datetime module to work with time zones in Python. It creates different time zone objects, instantiates datetime objects with and without time zone information, and demonstrates how to convert datetime objects between different time zones using the astimezone() method.

Question 27

Q

Challenge 1: Create a variable named moscow that holds a datetime.timezone object at +4 hours.

Challenge 2: Now create a timezone variable named pacific that holds a timezone at UTC-08:00.

Challenge 3: Finally, make a third variable named india that hold’s a timezone at UTC+05:30.

Answer

A

Challenge 1:
~~~
import datetime
moscow = datetime.timezone(datetime.timedelta(hours=+4))
~~~

Challenge 2:
~~~
import datetime
moscow = datetime.timezone(datetime.timedelta(hours=+4))
pacific = datetime.timezone(datetime.timedelta(hours=-8))
~~~

Challenge 3:
~~~
import datetime
moscow = datetime.timezone(datetime.timedelta(hours=+4))
pacific = datetime.timezone(datetime.timedelta(hours=-8))
india = datetime.timezone(datetime.timedelta(hours=+5, minutes=+30))
~~~

Question 28

Q

Challenge 1:
naive is a datetime with no timezone.

Create a new timezone for US/Pacific, which is 8 hours behind UTC (UTC-08:00).

Then make a new variable named hill_valley. Copy the datetime info from naive and add the tzinfo attribute with the US/Pacific timezone you made.

Challenge 2:
Great, but the tzinfo attribute just sets the timezone, it doesn’t move the datetime to the new timezone. Let’s move one.

Make a new timezone that is UTC+01:00 and set it to a variable called tz.

Create a new variable named paris that uses hill_valley and the astimezone() method to change hill_valley to the new timezone.

Answer

A

Challenge 1:
~~~
import datetime

US_Pacific = datetime.timezone(datetime.timedelta(hours=-8))
naive = datetime.datetime(2015, 10, 21, 4, 29)
hill_valley = datetime.datetime(2015, 10, 21, 4, 29, tzinfo=US_Pacific)
~~~

Challenge 2:
~~~
import datetime

US_Pacific = datetime.timezone(datetime.timedelta(hours=-8))
naive = datetime.datetime(2015, 10, 21, 4, 29)
hill_valley = datetime.datetime(2015, 10, 21, 4, 29, tzinfo=US_Pacific)

tz = datetime.timezone(datetime.timedelta(hours=+1))
paris = hill_valley.astimezone(tz)
~~~

Question 29

Q

What is pytz and how to use it?

Answer

A

pytz is a third-party Python library that provides support for working with time zones. It is widely used and considered a standard library for dealing with time zones in Python.

The built-in datetime module in Python provides basic date and time functionality, but it has limited support for time zones. pytz extends the capabilities of the datetime module by offering a comprehensive and updated time zone database along with various tools and utilities.

Some key features of pytz include:

Time zone database: pytz includes an extensive database of time zones, which is regularly updated to incorporate changes in time zone rules, daylight saving time transitions, and historical time zone information.
Time zone conversion: pytz provides functions to convert datetime objects between different time zones accurately.
Localized date and time: pytz allows you to localize datetime objects to a specific time zone, making it easier to handle date and time information in different regions.
Time zone-aware arithmetic: pytz provides utilities to perform arithmetic operations with time zone-aware datetime objects, taking into account daylight saving time changes and other time zone rules.

Using pytz, you can handle complex time zone-related tasks, such as converting between different time zones, calculating time differences, and accounting for daylight saving time transitions. It is a valuable tool for working with dates, times, and time zones in Python.

To use pytz in your Python code, you first need to install the library. You can install it using pip by running the following command:

pip install pytz

Once pytz is installed, you can import it into your Python script and start using its features. Here’s an example of how to use pytz:

```python
import datetime
import pytz

Get the current UTC datetime
utc_now = datetime.datetime.now(pytz.utc)
print(“Current UTC datetime:”, utc_now)

Convert UTC datetime to a specific time zone
pacific = pytz.timezone(‘US/Pacific’)
pacific_now = utc_now.astimezone(pacific)
print(“Current Pacific time:”, pacific_now)

Create a datetime object in a specific time zone
paris = pytz.timezone(‘Europe/Paris’)
paris_time = datetime.datetime(2023, 6, 15, 12, 0, tzinfo=paris)
print(“Paris time:”, paris_time)

Convert a datetime object to a different time zone
sydney = pytz.timezone(‘Australia/Sydney’)
sydney_time = paris_time.astimezone(sydney)
print(“Sydney time:”, sydney_time)
~~~

In the above example:

We import datetime and pytz modules.
We get the current UTC datetime using datetime.datetime.now(pytz.utc).
We convert the UTC datetime to the Pacific time zone using astimezone().
We create a datetime object representing a specific time in the Paris time zone.
We convert the Paris datetime to the Sydney time zone using astimezone().

By utilizing pytz functions and methods, you can work with time zones, convert between different time zones, and perform various operations with time zone-aware datetime objects.

Question 30

Q

Explain each line of this REPL code in detail:

import datetime
import pytz
pacific = pytz.timezone("US/Pacific")
eastern = pytz.timezone("US/Eastern")
indian = pytz.timezone('Asia/Kolkata')
fmt = '%Y-%m-%d %H-%M-%S %Z%z' #%Z%z gives timezone with offset like IST-UTC+5.30
utc = pytz.utc
start = pacific.localsize(datetime.datetime(2014, 4, 21, 9))
start.strftime(fmt)
start_eastern = start.astimezone(eastern)
start_eastern
start_utc = datetime.datetime(2014, 4, 21, 1, tzinfo=utc)
start_utc.strftime(fmt)
start_pacific = start.utc.astimezone(pacific)
current = datetime.datetime.now(pytz.utc)
current.strftime(fmt)
current_indian = current.astimezone(indian)
current_indian
apollo_13_naive = datetime.datetime(1970, 4, 11, 14, 13)
apollo_13_naive
apollo_13_indian = indian.localize(apollo_13_naive)
apollo_13_indian
apollo_13_eastern = eastern.localize(apollo_13_naive)
apollo_13_eastern
apollo_13_utc = apollo_13_eastern.astimezone(utc) #can't use naive directly because it doesn't know the timezone so using eastern instead
apollo_13_utc
apollo_13_utc.astimezone(pacific).strftime(fmt)
apollo_13_utc.astimezone(indian).strftime(fmt)
pytz.all_timezones
pytz.country_timezones['us']

Answer

A

Let’s go through each line of the code and explain its purpose:

import datetime: Imports the built-in datetime module, which provides classes for manipulating dates and times.
import pytz: Imports the pytz library, which provides support for working with time zones.
pacific = pytz.timezone("US/Pacific"): Creates a timezone object named pacific representing the US Pacific time zone.
eastern = pytz.timezone("US/Eastern"): Creates a timezone object named eastern representing the US Eastern time zone.
indian = pytz.timezone('Asia/Kolkata'): Creates a timezone object named indian representing the time zone for Kolkata, India.
fmt = '%Y-%m-%d %H-%M-%S %Z%z': Defines a format string for date and time formatting. %Z represents the time zone name, and %z represents the time zone offset.
utc = pytz.utc: Assigns the utc variable with the timezone object representing Coordinated Universal Time (UTC).
start = pacific.localsize(datetime.datetime(2014, 4, 21, 9)): Creates a datetime object named start representing April 21, 2014, 09:00 in the US Pacific time zone.
start.strftime(fmt): Formats the start datetime object using the specified format string and returns a formatted string representation of the datetime.
start_eastern = start.astimezone(eastern): Converts the start datetime object from the US Pacific time zone to the US Eastern time zone.
start_eastern: Prints the start_eastern datetime object, which represents the converted time in the US Eastern time zone.
start_utc = datetime.datetime(2014, 4, 21, 1, tzinfo=utc): Creates a datetime object named start_utc representing April 21, 2014, 01:00 in the UTC time zone.
start_utc.strftime(fmt): Formats the start_utc datetime object using the specified format string and returns a formatted string representation of the datetime.
start_pacific = start.utc.astimezone(pacific): Converts the start datetime object from the UTC time zone to the US Pacific time zone.
current = datetime.datetime.now(pytz.utc): Gets the current datetime in UTC using the datetime.now() method with the UTC time zone specified.
current.strftime(fmt): Formats the current datetime object using the specified format string and returns a formatted string representation of the datetime.
current_indian = current.astimezone(indian): Converts the current datetime object from the UTC time zone to the Kolkata, India time zone.
current_indian: Prints the current_indian datetime object, which represents the converted current time in the Kolkata, India time zone.
apollo_13_naive = datetime.datetime(1970, 4, 11, 14, 13): Creates a naive datetime object named apollo_13_naive representing April 11, 1970, 14:13 without a specified time zone.
apollo_13_indian = indian.localize(apollo_13_naive): Localizes the apollo_13_naive datetime object to the Kolkata, India time zone using the localize() method.
`apollo_

13_indian: Prints the apollo_13_indian` datetime object, which represents the localized time in the Kolkata, India time zone.

apollo_13_eastern = eastern.localize(apollo_13_naive): Localizes the apollo_13_naive datetime object to the US Eastern time zone using the localize() method.
apollo_13_eastern: Prints the apollo_13_eastern datetime object, which represents the localized time in the US Eastern time zone.
apollo_13_utc = apollo_13_eastern.astimezone(utc): Converts the apollo_13_eastern datetime object from the US Eastern time zone to the UTC time zone using the astimezone() method.
apollo_13_utc: Prints the apollo_13_utc datetime object, which represents the converted time in the UTC time zone.
apollo_13_utc.astimezone(pacific).strftime(fmt): Converts the apollo_13_utc datetime object from the UTC time zone to the US Pacific time zone and formats it using the specified format string.
apollo_13_utc.astimezone(indian).strftime(fmt): Converts the apollo_13_utc datetime object from the UTC time zone to the Kolkata, India time zone and formats it using the specified format string.
pytz.all_timezones: Retrieves a list of all available time zone names supported by pytz.
pytz.country_timezones['us']: Retrieves a list of time zone names associated with the country code ‘us’ (United States) using the country_timezones dictionary.

The code demonstrates various operations with time zones, including converting between different time zones, formatting datetime objects, and working with naive and localized datetime objects using pytz functions and methods.

Question 31

Q

Challenge: Use pytz to build a script that takes time in your timezone and then gives that time back in 6 other timezones using our format string (fmt = '%Y-%m-%d %H:%M:%S %Z%z')

Answer

A

The code is:

from datetime import datetime

import pytz

OTHER_TIMEZONES = [
    pytz.timezone('US/Eastern'),
    pytz.timezone('Pacific/Auckland'),
    pytz.timezone('Asia/Calcutta'),
    pytz.timezone('UTC'),
    pytz.timezone('Europe/Paris'),
    pytz.timezone('Africa/Khartoum')
]
fmt = '%Y-%m-%d %H:%M:%S %Z%z' 

while True:
    date_input = input("When is your meeting? Please use MM/DD/YYYY HH:MM format. ")
    try:
        local_date = datetime.strptime(date_input, '%m/%d/%Y %H:%M')
    except ValueError:
        print("{} doesn't seem to be a valid date & time.".format(date_input))
    else:
        local_date = pytz.timezone('US/Pacific').localize(local_date)
        utc_date = local_date.astimezone(pytz.utc)
        
        output = []
        for timezone in OTHER_TIMEZONES:
            output.append(utc_date.astimezone(timezone))
        for appointment in output:
            print(appointment.strftime(fmt))
        break

Question 32

Q

Challenge 1: starter is a naive datetime. Use pytz to make it a “US/Pacific” datetime instead and assign this converted datetime to the variable local.

pytzstring.py
~~~
import datetime

fmt = ‘%m-%d %H:%M %Z%z’
starter = datetime.datetime(2015, 10, 21, 4, 29)
~~~

Challenge 2: Now create a variable named pytz_string by using strftime with the local datetime. Use the fmt string for the formatting.

Answer

A

Challenge 1:
~~~
import datetime
import pytz

fmt = ‘%m-%d %H:%M %Z%z’
starter = datetime.datetime(2015, 10, 21, 4, 29)
pacific = pytz.timezone(“US/Pacific”)
local = pacific.localize(starter)
~~~

Challenge 2:
~~~
import datetime
import pytz

fmt = ‘%m-%d %H:%M %Z%z’
starter = datetime.datetime(2015, 10, 21, 4, 29)
pacific = pytz.timezone(“US/Pacific”)
local = pacific.localize(starter)
pytz_string = local.strftime(fmt)
~~~

Question 33

Q

What is the difference between this two in python?

import datetime
from datetime import datetime

Answer

A

In Python, both statements involve importing the datetime module, but there is a difference in how the datetime object is accessed.

import datetime: This statement imports the entire datetime module into your current namespace. To access the datetime object or any other objects within the module, you need to prefix them with the module name. For example, to use the datetime object, you would write datetime.datetime.
from datetime import datetime: This statement imports only the datetime object from the datetime module directly into your current namespace. It allows you to use the datetime object directly without having to prefix it with the module name. So, you can simply use datetime to access the datetime object.

Here’s an example to illustrate the difference:

```python
# Example 1: import datetime
import datetime

current_date = datetime.datetime.now()
print(current_date)

Example 2: from datetime import datetime
from datetime import datetime

current_date = datetime.now()
print(current_date)
~~~

In both examples, we are using the now() method of the datetime object to get the current date and time. However, in the first example, we need to use datetime.datetime.now(), whereas in the second example, we can directly use datetime.now() because we imported the datetime object directly.

Question 34

Q

Explain the following code:

from datetime import datetime
import pytz

OTHER_TIMEZONES = [
    pytz.timezone('US/Eastern'),
    pytz.timezone('Pacific/Auckland'),
    pytz.timezone('Asia/Calcutta'),
    pytz.timezone('UTC'),
    pytz.timezone('Europe/Paris'),
    pytz.timezone('Africa/Khartoum')
]

fmt = '%Y-%m-%d %H:%M:%S %Z%z'

while True:
    meeting_date = input('Enter the meeting date in format MM/DD/YYYY HH:MM. ')
    try:
        local_date = datetime.strptime(meeting_date, '%m/%d/%Y %H:%M')
    except ValueError:
        print('{} is invalid, try again!'.format(meeting_date))
    else:
        local_date = pytz.timezone('Asia/Calcutta').localize(local_date)
        utc_date = local_date.astimezone(pytz.utc)
        
        output = []
        for timezone in OTHER_TIMEZONES:
            output.append(utc_date.astimezone(timezone))
        for appointment in output:
            print(appointment.strftime(fmt))
        break

Answer

A

Certainly! Let’s break down the code and go through each step in more detail:

Importing modules:
```
python
from datetime import datetime
import pytz
```
The code begins by importing two modules: datetime and pytz. The datetime module provides classes for manipulating dates and times, while pytz is a third-party library that allows working with time zones.
Defining time zones:
```
python
OTHER_TIMEZONES = [
    pytz.timezone('US/Eastern'),
    pytz.timezone('Pacific/Auckland'),
    pytz.timezone('Asia/Calcutta'),
    pytz.timezone('UTC'),
    pytz.timezone('Europe/Paris'),
    pytz.timezone('Africa/Khartoum')
]
```
Here, a list named OTHER_TIMEZONES is defined, which contains several time zones specified as pytz.timezone objects. These time zones include ‘US/Eastern’, ‘Pacific/Auckland’, ‘Asia/Calcutta’, ‘UTC’, ‘Europe/Paris’, and ‘Africa/Khartoum’.
Defining date format:
```
python
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
```
The variable fmt is assigned a string value representing the desired date and time format. It specifies the format as ‘%Y-%m-%d %H:%M:%S %Z%z’, where:
- %Y represents the four-digit year
- %m represents the two-digit month
- %d represents the two-digit day
- %H represents the hour in 24-hour format
- %M represents the minute
- %S represents the second
- %Z represents the time zone name
- %z represents the time zone offset from UTC
Entering a meeting date:
```
python
while True:
    meeting_date = input('Enter the meeting date in format MM/DD/YYYY HH:MM. ')
    try:
        local_date = datetime.strptime(meeting_date, '%m/%d/%Y %H:%M')
    except ValueError:
        print('{} is invalid, try again!'.format(meeting_date))
    else:
        # Code continues...
```
The code enters an infinite while loop to repeatedly ask the user to enter a meeting date in the specified format ‘MM/DD/YYYY HH:MM’. The input() function is used to receive the user’s input.Inside the loop, the entered meeting_date string is parsed and converted to a datetime object using datetime.strptime(). If the entered date does not match the expected format, a ValueError is raised, and the program displays an error message. Otherwise, if the date is valid, the program proceeds to the next steps.
Converting to the ‘Asia/Calcutta’ time zone:
```
python
    local_date = pytz.timezone('Asia/Calcutta').localize(local_date)
```
After successfully parsing the meeting date, the code converts the local_date to the ‘Asia/Calcutta’ time zone using the localize() method of the pytz.timezone('Asia/Calcutta') object.
Converting to UTC time zone:
```
python
    utc_date = local_date.astimezone(pytz.utc)
```
The localized local_date is then converted to the UTC time zone using the astimezone() method with pytz.utc. This step ensures that the meeting date is represented in UTC, which

serves as a common reference time zone.

Generating appointment times in different time zones:
```
python
    output = []
    for timezone in OTHER_TIMEZONES:
        output.append(utc_date.astimezone(timezone))
```
An empty list named output is created to store the converted appointment times in different time zones. The code iterates through each timezone in the OTHER_TIMEZONES list and converts the utc_date to the respective time zone using the astimezone() method. The converted appointment times are then appended to the output list.
Displaying appointment times:
```
python
    for appointment in output:
        print(appointment.strftime(fmt))
```
The code loops over each appointment in the output list and prints the formatted appointment time using the strftime() method. The strftime() function formats the appointment time according to the fmt format specified earlier. The appointment times are displayed for each time zone defined in OTHER_TIMEZONES.
Exiting the loop:
```
python
    break
```
After displaying the appointment times for all the time zones, the break statement is encountered, which exits the while loop, effectively ending the program.

In summary, this code allows the user to enter a meeting date and time, converts it to the specified time zones, and then displays the corresponding appointment times in those time zones. It utilizes the datetime and pytz modules to handle date and time operations, as well as time zone conversions.

Question 35

Q

Challenge: Create a function named to_timezone that takes a timezone name as a string. Convert starter to that timezone using pytz’s timezones and return the new datetime.

import datetime

import pytz

starter = pytz.utc.localize(datetime.datetime(2015, 10, 21, 23, 29))

Answer

A

Answer:

import datetime
import pytz

starter = pytz.utc.localize(datetime.datetime(2015, 10, 21, 23, 29))

def to_timezone(timezone):
    target_tz = pytz.timezone(timezone)
    result = starter.astimezone(target_tz)
    return result

Question 36

Q

Does the datetime methods .today() and .now() give back the same values by default? Explain

Answer

A

Yes, that’s correct. In Python, the datetime.today() and datetime.now() methods generally provide the same value by default, which is the current date and time.

Both methods are available in the datetime module. Here’s a brief explanation of each method:

datetime.today(): This method returns the current local date and time as a datetime object. The local time is determined by the system’s time zone settings.
datetime.now(): This method also returns the current local date and time as a datetime object. Like datetime.today(), it uses the system’s time zone settings.

The main difference between datetime.today() and datetime.now() lies in their optional tz parameter:

datetime.today(tz=None) does not accept a tz parameter and always returns the local date and time based on the system’s time zone settings.
datetime.now(tz=None) accepts an optional tz parameter that allows you to specify a specific time zone to obtain the current date and time. If tz is None, it behaves the same as datetime.today().

Here’s an example to illustrate their usage:

```python
from datetime import datetime

current_datetime1 = datetime.today()
current_datetime2 = datetime.now()

print(“datetime.today():”, current_datetime1)
print(“datetime.now(): “, current_datetime2)
~~~

Both current_datetime1 and current_datetime2 will generally have the same value, representing the current local date and time.

Question 37

Q

What pytz method is used to convert a naive datetime to an aware one? localise or astimezone?

Answer

A

In the pytz library, the method used to convert a naive datetime object to an aware one is localize(). The localize() method assigns a timezone to a naive datetime object, making it aware of the timezone.

Here’s an example of how you can use localize() to convert a naive datetime object to an aware one:

```python
import datetime
import pytz

Create a naive datetime object
naive_dt = datetime.datetime(2023, 6, 15, 10, 30)

Create a timezone object
timezone = pytz.timezone(‘America/New_York’)

Convert the naive datetime to an aware one
aware_dt = timezone.localize(naive_dt)

print(aware_dt)
~~~

Output:
~~~
2023-06-15 10:30:00-04:00
~~~

In contrast, the astimezone() method is used to convert an aware datetime object from one timezone to another. It adjusts the datetime object’s timezone without changing the underlying datetime value.

It’s important to note that localize() is used specifically for assigning a timezone to a naive datetime object, while astimezone() is used for converting an aware datetime object from one timezone to another.

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