Learn Python Quickly

Question 1

exit()

Answer 1

exited with the quit command or depending on the version you are running quit()

Question 2

help()

Answer 2

all the various commands

Question 3

> > >

Answer 3

The primary prompt. Python is waiting for a command when you see this.

Question 4

…

Answer 4

Python is waiting for your input, but this means it’s the second line of input

Question 5

IDE

Answer 5

Most programming done in the IDE (integrated development environment). They auto complete commands, phrases, and functions, track bugs, highlight syntax errors and overall make programming and seeing the output of your programs easier.

Question 6

Book recommends which IDEs?

Answer 6

PyCharm, Spyder, PyDev, Idle, and Wing.

Question 7

writing comments in python

Answer 7

use # at the start of a line or
Triple single quotes at the start and end of your multi-line statement:
‘’’
comment 1
2
3
‘’’

Question 8

variables: how to assign string variables?

Answer 8

use “
stuff = “cloudy”

Question 9

Python Operators

Answer 9

• Operators are symbols that perform functions and are used to manipulate data in different ways

Question 10

Example operators

Answer 10

Operators:
- assignment is the = for assigning variables
- R = 12
- S = 5
- T = S
- ^^ assigning variable to a variable

• Addition: +
  
  • R + S = 17
• Subtraction: -
  
  • R - S = 7
• Multiplication: *
  R * S = 60
• Division: /
  
  • R / S = 2.4
• Floor division: //
  
  • This divides and then rounds down to the nearest whole number
  • R // S = 2
• Modulus (mod): %
  
  • Modulus operator produces the remainder of the division operation
  • R % S = 2
• Exponent: **
  
  • R ** S is R to the S power
  • R ** S = 248,832

R = 12
S = 5

Question 11

• Floor division:

Answer 11

//
- This divides and then rounds down to the nearest whole number
- R // S = 2
R = 12
S = 5

Question 12

• Modulus (mod):

Answer 12

%
- Modulus operator produces the remainder of the division operation
- R % S = 2
R = 12
S = 5

Question 13

• Exponent:

Answer 13

**
- R ** S is R to the S power
- R ** S = 248,832
R = 12
S = 5

Question 14

Can you combine operators?

Answer 14

Yes. Specifically this way:
Short handing R = R * 2
shrinks to R * = 2

Same for the other operators

Question 15

Variables are stored as what primary Data Types in Python?

Answer 15

Primary Data types:
- integers
- floats
- strings

Question 16

What are the the different data structures used for the primary data type variables?

Answer 16

• lists
• tuples
• dictionaries

Question 17

Integers

Answer 17

• same as math class
• whole numbers
• positive or negative
• assigns normally to a variable

Question 18

floats

Answer 18

• Numbers that contain decimal parts
• positive or negative
• assigns normally to a variable

Question 19

strings

Answer 19

• text data
• assign them using “ “ or ‘ ‘
• string_1 = “string”

Question 20

What order should nested quotes be used inside strings?

Answer 20

• Use “ “ first, then ‘ ‘ inside the quoted space

Question 21

How are numbers treated in a quote do when assigned to a variable?
A = “12”

Answer 21

Python sees them as a string.

Question 22

String Manipulation

Answer 22

• you can combine them the same way we combine numbers:
  str_1 = “Words “
  str_2= “and “
  str_3= “more words.”

str_4 = str_1 + str_2 + str_3
print(str_4)

Running this =
Words and more words.

Question 23

changing letter case using built in functions. Explain upper and lower case usage with string variables.

Answer 23

Using the following functions will change the letter case to upper or lower:
my_up_string = “all MY letters”.upper()
my_dn_string2 = “ all MY letters”.lower()

print(my_up_string + my_dn_string2)

running this =
ALL MY LETTERS all my letters

Question 24

String formatting example using %

Answer 24

Using mod operator % on strings allows you to specify values / variables you would like to insert into a string.

string = “With the mod op, you can add %s, integers like %d, or even floats like %2.1f.”%(“strings”, 25, 12.34)

print (string)

running this =
With the mod op, you can add strings, integers like 25, or even floats like 12.3.

where every % gets its variable / value piped in from the entries at the end of the variable assignment line. special notes here:
- %s is a string
- %d is an integer (digit?)
- %f is a float, but in this instance we used %2.1f
- %2.1f took the 12.34 and read it as needing 2 digits before the decimal place and one digit after the decimal place resulting in 12.3

Question 25

Automatic formatting example using {}

Answer 25

There’s more on this later in the chapter, but using the format function for strings instead of using the modulus operator.
- Inside the brackets goes:
- data type tag
- position of the value in the collection of values you want in that spot
- it is possible to leave the brackets blank. Python will automatically fill them in from left to right with the values listed left to right.

“The string you want to format {} “.format(values you want to insert)
- curly braces denote the location where you want to insert the value.
- to insert multiple values, you need to create multiple braces then separate the values with commas

string = “with the mod operator, you can add {0:s}, integers like {1:d}, or even floats like {2:2.2f}”

print (string.format(“strings”, 25, 12.34))

will print =
with the mod operator, you can add strings, integers like 25, or even floats like 12.3

Question 26

Python starts with 0 or 1?

Answer 26

Unlike some other programming languages, python is a zero-based system when it comes to positions. First position is ZERO, second is ONE.

Question 27

what is Type Casting used for?

Answer 27

Converting data from one type to another type.
e.g. String to Integer

Question 28

int()

Answer 28

convert to integer
- going FLOAT to INTEGER means it will drop the decimal values and always round down to the whole number value
- strings to integers obviously need to be numbers

Question 29

float()

Answer 29

convert to float
strings to floats obviously need to be numbers.

Question 30

str()

Answer 30

convert to string
basically anything can become a string.

Question 31

Data Structures?

Answer 31

How data is stored.

Question 32

what are the different data structures in python?

Answer 32

Lists
Tuples
Dictionaries

Question 33

Lists

Answer 33

Data structure
Collections of data
quick and easy storage and retrieval of items
Functionally this is done by saving the list as a variable that’s declared as a list

Question 34

List: syntax example of a list

Answer 34

Fruits = [“apple”,”pear”,”coconut”]

Question 35

List: Can you declare an empty list to append items to later?

Answer 35

yes
Fruits = []
append() to add more later

Question 36

List: How do you access a specific item in the list?

Answer 36

when the list is:
Fruits = [“apple”,”pear”,”coconut”]

then the first item is:
apple = fruits[0]

Question 37

List: call something from the end or second to last of the list

Answer 37

Fruits = [“apple”,”pear”,”coconut”]

last = Fruits[-1]
seclast = Fruits[-2]
print(last)
print(seclast)

Using slicing.
a[-1] # last item in the array
a[-2:] # last two items in the array
a[:-2] # everything except the last two items

Question 38

List: How do you call multiple items from a list?

Answer 38

Using slicing.
where a = a list
a[start:stop:step]
start through not past stop, by step

a[start:stop]
items start through stop-1
a[1:5], will print items 1 through 4

a[start:]
items start through the rest of the array

a[:stop]
items from the beginning through stop-1

a[:]
a copy of the whole array

Question 39

List: Reversing the order of items in a list

Answer 39

a[::-1] # all items in the array, reversed
a[1::-1] # the first two items, reversed
a[:-3:-1] # the last two items, reversed
a[-3::-1] # everything except the last two items, reversed

Question 40

List: in what ways are lists modified?

Answer 40

add, remove, and values can be altered

Question 41

List: How to append lists?

Answer 41

list_to_append.append(value)
where
value = item number (starting at 0)

Question 42

List: How to remove items from lists?

Answer 42

list_to_append.remove(value)
where
value = item number (starting at 0)

Question 43

List: How to remove items from lists?

Answer 43

To remove a single entry:
list_to_append.remove(value)
where
value = item number (starting at 0)

to remove multiple entries at once:
del List_Name[2:4]
which will delete everything from the 3rd item through the 4th item

Question 44

list: how to edit the 2nd through the 4th items in a list

Answer 44

Fruits[1:4] = [“pear1”,”coconut1”,”riot1”]

Question 45

list: how to insert items into a list

Answer 45

list_name.insert(Where,Inserted_Item)

a.insert(1,”outland”)
Inserts outland string before list item 1, but after list item 0 and pushing everything else after it down the list

Question 46

Whats the difference between lists and arrays?

Answer 46

Lists are basically the same as other arrays outside of python.

Python do have arrays too, they are more functional than lists if you want to say divide everything in the array by 4. Doing this with lists will result in an error.

Question 47

Tuples: What are tuples?

Answer 47

Similar to lists, but can’t be modified

Question 48

Tuples: when would Tuples be beneficial?

Answer 48

Whenever you have an unchanging list of items. Examples include the days of the week, Months, etc.

Question 49

Tuples: How do you define Tuples in py?

Answer 49

MyTuple = (“Mon”,”Tue”,”Wed”)

Using parenthesis instead of brackets.

Question 50

Tuples: How are Tuples called / accessed in py?

Answer 50

Same as lists

Question 51

Dictionaries: what are they?

Answer 51

Dictionaries hold data that can be retrieved with reference items or keys

They contain pairs of keys and values associated with those keys

Question 52

Dictionaries: Can you have 1 key open multiple box

Answer 52

No that would be problematic. e.g. 2 keys both named cyfer1

Question 53

Dictionaries: How do you create a key in py?

Answer 53

Use curly braces containing the key on the left side and the value on the right side.
separated by a colon.

dict_example = {“key0”:39, “key1”:50}

or by using the dict() method
dict_example2 = dict(key0 = 39, key1 = 21)

Question 54

Dictionaries: How do you access the items in one?

Answer 54

dictionary[‘key’]

(Bracket, single quote surrounding key value)

example:
dict_example2 = dict(key0 = 39, key1 = 21)

dict_example2[‘key0’]

would resolve to 39

Question 55

Dictionaries: Can you define an empty one? If so how?

Answer 55

dict_example2 = {}

To add data to the dictionary, just assign a value:
dict_example2 [“key1”] = 60

Question 56

Dictionaries: how do you add entries?

Answer 56

To add data to the dictionary, just assign a value to key
dict_example2 [‘key1’] = 60

Question 57

Dictionaries: how do you remove entries?

Answer 57

del dict_example2[‘key0’]

Would remove the value associated to key0

Question 58

Inputs: How do you solicit and accept input from the user?

Answer 58

the input() function
similar to read -p command in bash

Question 59

Inputs: How to store a variable using input()

Answer 59

food = input(“What food do you want?:\n”)

Question 60

Variables: Best way to print two variables using f-string formatting?

Answer 60

(f-string formatting is available in Python 3.6)
example:
name = “fine”
score = 20
print(f’Grand total for {name} is {score}’)

Question 61

Print: How can you print out less wide blocks of text without using /n?

Answer 61

example:
use triple single quotes and enter between lines to space it however you wish:

longstring = ‘'’Using triple quotes will allow us to
divid our statements onto multiple lines This makes
it easier to read As you can see this shrinks up the
output…’’’
print(f’{longstring}’)

Question 62

Print: how to use raw string formatter as an escape on an entire string?

Answer 62

escape character r or R

example:
This applies to the entire string:
print(r”hey hey \t we’re the monkeys.”)
print(R”hey hey \t we’re the monkeys.”)

normal print
print(“hey hey \t we’re the monkeys.”)

Question 63

Print: how to avoid a long string from running across the screen?

Answer 63

Use triple ‘ to surround the string and apply normal text editing with new lines and tabs.
example:
print(‘’’hey there
How’s it going?
Oh that’s good!‘’’

Question 64

Delete

Question 65

Print: how do you print more than one string in a print or input function?

Answer 65

You can using the format function.
Example:
name = “B”
nametwo = “john”
foodtwo = input(“What food does {0} want and what kind does {1} want?:\n”.format(name,nametwo))

Question 66

Print: how to use an escape character on a specific item WITHOUT using raw string formatter on the entire string?

Answer 66

example:
use \
print(“hey hey \\t we’re the monkeys.”)