Part 4 Modules

Question 1

Import a module to display current time

Answer 1

import datetime

x = datetime.datetime.now()

Question 2

There is a method in the datetime module that outputs more human readable formats but requires DIRECTIVES. Use it, but first pass the year 2018, the month June and the day 1 to it.

Answer 2

x = datetime.datetime(2018, 6, 1)
x.strftime((‘%B’))

%B - this is the directive
strftime <- string format time

Question 3

Show the absolute value of -17
show the lowest and highest values of the below list:
[5, 10, 48]

Calculate the value of 4 to the power of 3

Answer 3

print(abs(-7.25))

print(min(5, 10, 48))
print(max(5, 10, 48))
print(pow(4, 3)
This basically means 3 over for or (4 * 4 * 4)

Question 4

Import a module to:
determine the square root of 64

round 1.4 to the upwards to the nearest integer and then downward to the

show the value of pi

Answer 4

import math
print(math.sqrt(64))

math.ceil(1.4)
math.floor(1.4)

math.pi

Question 5

What does JSON stand for?
Import JSON and:
Create a variable that looks like JSON
Parse it
Print the results

Answer 5

Java Script Object Notation

import json

x = ‘{ ‘name’: ‘John’, ‘age’ : 30, ‘city’: ‘New York}’

y = json.loads(x)

print(y[‘age’])

parsing - divide something into parts to analyze individually
data parsing - Converting one data format to another

Question 6

Convert the below python into json

x = { ‘name’: ‘John’, ‘age’: 30, ‘city’: ‘New York’}

Answer 6

import json
y = json.dumps(x)
print(y)

Question 7

What are the json equivalents to the below
dict
list
tuple
str
int
float
True
False
None

Answer 7

Python JSON
dict Object
list Array
tuple Array
str String
int Number
float Number
True true
False false
None null

Question 8

Via the json module, convert a dictionary named ‘x’ into json format, giving an indentation for 4 spaces for readability.

Answer 8

json.dumps(x, indent=4)

Question 9

JSON normally indents using a comma and a space to separate each object and a colon and a space to separate keys from values, how would you change this

Also, how would you sort the keys?

Answer 9

json.dumps(x, indent=4, separators=(‘. ‘, ‘=’)

json.dumps(x, indent=4, sort_keys=True

Question 10

In JSON, what are dictionaries called?

Answer 10

Objects
{‘key’:’value’}

Question 11

Import regular expessions
Search the below string to see if it starts with “The” and ends with ‘Spain’

x = The rain in Spain

Answer 11

import re

txt = ‘The rain in Spain’
x = re.search(‘^The.*Spain$’, txt)

^ <- starts with
$ <- ends with
.* <- match any characters (zero or more)

Question 12

What is PIP

Answer 12

PIP is python’s package manager

you can find pip packages at:
https://pypi.org/

Question 13

How do you install and uninstall a pip package

Answer 13

pip install package
pip uninstall package

Question 14

List all pip packages on your system

Answer 14

pip list

Question 15

Your code does not contain an x variable. This would normally stop the code in its tracks. How would you keep the code functioning despite this error.

If you know the answer, handle two errors.

Answer 15

try:
print(x)
except NameError:
print(“Variable x not defined”)
except:
print(“Something else went wrong”)

Question 16

Handle an error
Add a block of code that prints a message if there is no error and also if there is one.

Answer 16

try:
print(‘hello’)
except:
print(‘error’)
else:
print(‘no error’)

Question 17

What is a good use case for ‘finally’?

Answer 17

If you’ve opened a file, you’ll want to close it regardless of a success. The ‘with’ statement will also do this.

Question 18

Create an exception error, then create a TypeError

Answer 18

raise Exception(‘Sorry, no numbers below zero.’)

raise TypeError(‘only integers are allowed’)

If you raise the ‘TypeError’ here your code will lump that in with other TypeErrors, allowing you to handle it later with except TypeError: in the future.

Example:

a = input(‘input the number 5’)
a = int(a)
if a != 5:
raise Exception(‘The number is not 5’)

Question 19

Why would you use raise?

Answer 19

It creates an exception where there wouldn’t normally be.

After this step you can move on to exception handling, so the code breaks out to where nothing will break or not function properly eventually.

f you raise the ‘TypeError’ here your code will lump that in with other TypeErrors, allowing you to handle it later with except TypeError: in the future.

Question 20

Gather user stdin and place it in a variable

Answer 20

username = input(‘Enter your username’)

Question 21

For file handling, you use the ‘open()’ function where you insert a ‘filename’ and a ‘mode’.

What are all the modes you can use?

Answer 21

‘r’ - read
‘a’ - append, creates file if it does not exist
‘w’ - write
‘x’ - create, returns error if file exists

additionals:
‘t’ - text mode
‘b’ - binary mode

Question 22

create a variable that opens ‘demofile.txt’ in text mode to read

Now actually use a function to read it.

Answer 22

f = open(‘demofile.txt’, ‘rt’)

print(f.read())

Question 23

You’ve opened a file to read which is stored in the variable ‘f’

Return only the first 5 characters.

return only one line from a file, then the next

Close the file after you are done with it.

Answer 23

f = open(‘demofile.txt’, ‘r’)
print(f.read(5))

print(f.readline(), f.readline())

f.close()

Question 24

Open a file, append something to it, close it, then read it

Answer 24

f = open(‘demofile.txt’, ‘a’)
f.write(‘new line’)
f.close

f = open(‘demofile.txt’, ‘r’)
print(f.read())

Question 25

How do you completely overwrite a file?

Answer 25

f.write()

Question 26

Removing a file is a slightly different process.

Delete the file ‘demofile.txt’

It might be better to check if the file exists first as to not raise an error.

Now Delete an entire folder named ‘myfolder’ (Only removes empty folders.)

Answer 26

import os
if os.path.exists(‘demofile.txt’):
os.remove(‘demofile.txt’)
else:
print(‘the file does not exist.’)

os.rmdir(‘myfolder’)