Best Python Cheatsheet: The Ultimate Guide to Learning Python (Updated 2022) | For Beginners and Experts Alike

Our easy to use python cheatsheet features all the commands in a unique and easy to read format. If you are an entrepreneur, student or looking for a new programming job, then you will love this cheatsheet.

Python 3 is a highly adaptable programming language that is preferred by a wide variety of developers, including software engineers, data scientists, and web developers. And there are many compelling reasons for that to be the case!

Python is a free and open-source programming language that has an active and helpful user community in addition to numerous support libraries.
It has data structures that are easy to navigate.

What is IDLE (Integrated Development and Learning)?

Every installation of Python includes a program known as IDLE, which stands for Integrated Development and Learning Environment.
It has a benefit over other text editors in that it highlights crucial terms, such as string functions, which makes it much simpler for you to understand the code.

Python’s Integrated Development Environment (IDLE) operates in the shell by default. In its most basic form, it is a loop that iteratively completes the following four tasks:

• Reads the Python statement
• Evaluates the results of it
• Prints the result on the screen
• And then loops back to read the next statement.

Python shell is a great place to test various small code snippets.

Variables

We use variables to temporarily store data in computer’s memory.
price = 10
rating = 4.9
course_name = ‘Python for Beginners’
is_published = True

In the above example,
• price is an integer (a whole number without a decimal point)
• rating is a float (a number with a decimal point)
• course_name is a string (a sequence of characters)
• is_published is a boolean. Boolean values can be True or False.

Data Types

Data TypeExamples
Integers-2, -1, 0, 1, 2, 3, 4, 5
Floating-point numbers-1.25, -1.0, --0.5, 0.0, 0.5, 1.0, 1.25
Strings'a', 'aa', 'aaa', 'Hello!', '11 cats'

Comments

Inline comment:

# This is a comment

Multiline comment:

# This is a
# multiline comment

Code with a comment:

a = 1  # initialization

Please note the two spaces in front of the comment.

Function docstring:

def foo():
    """
    This is a function docstring
    You can also use:
    ''' Function Docstring '''
    """

Also, Check out Data Structure Problem Solutions:

The print() Function

>>> print('Hello world!')
Hello world!
>>> a = 1
>>> print('Hello world!', a)
Hello world! 1

The input() Function

Example Code:

>>> print('What is your name?')   # ask for their name
>>> myName = input()
>>> print('It is good to meet you, {}'.format(myName))
What is your name?
Al
It is good to meet you, Al

The len() Function

Evaluates to the integer value of the number of characters in a string:

>>> len('hello')
5

Note: a test of the emptiness of strings, lists, dictionary, etc, should not use len, but prefer direct boolean evaluation.

>>> a = [1, 2, 3]
>>> if a:
>>>     print("the list is not empty!")

The str(), int(), and float() Functions

Integer to String or Float:

>>> str(29)
'29'
>>> print('I am {} years old.'.format(str(29)))
I am 29 years old.
>>> str(-3.14)
'-3.14'

Float to Integer:

>>> int(7.7)
7
>>> int(7.7) + 1
8

filter()

Use the Filter() function to exclude items in an iterable object (lists, tuples,
dictionaries, etc)

ages = [5, 12, 17, 18, 24, 32]
def myFunc(x):
    if x < 18:
        return False
    else:
        return True
adults = filter(myFunc, ages)
for x in adults:
    print(x)

Receiving Input

We can receive input from the user by calling the input() function.
birth_year = int(input(‘Birth year: ‘))

The input() function always returns data as a string. So, we’re converting the
result into an integer by calling the built-in int() function.

Strings

You can create a string in three ways using single, double, or triple quotes. Here’s an example of every option:

Basic Python String

my_string = “Let’s Learn Python!”
another_string = ‘It may seem difficult first, but you
can do it!’
a_long_string = ‘’’Yes, you can even master multi-line
strings
 that cover more than one line
 with some practice’’’

String Concatenation

The next thing you can master is concatenation — a way to add two strings
together using the “+” operator. Here’s how it’s done:

string_one = “I’m reading “
string_two = “a new great book!”
string_three = string_one + string_two

Note: You can’t apply + operator to two different data types e.g. string + integer. If you try to do that, you’ll get the following Python error:

TypeError: Can’t convert ‘int’ object to str implicitly

String replication

This command lets you repeat the same string several times, as the name suggests. The * operator is used to do this.

Keep in mind that this operator can only be used to copy string data types.
It acts as a multiplier when it is used with numbers.

Example of string replication:

‘Alice’ * 5 =‘AliceAliceAliceAliceAlice’ In Python

And with print ()

print(“Alice” * 5)

And your output will be Alice written five times in a row.

String Common Functions

We can use formatted strings to dynamically insert values into our strings:

name = ‘Mosh’
message = f’Hi, my name is {name}’
message.upper() # to convert to uppercase
message.lower() # to convert to lowercase
message.title() # to capitalize the first letter of every word
message.find(‘p’) # returns the index of the first occurrence of p
(or -1 if not found)
message.replace(‘p’, ‘q’)

To check if a string contains a character (or a sequence of characters), we use the in operator:

contains = ‘Python’ in the course

Math Operators

For reference, here’s a list of other math operations you can apply to numbers:

image

Flow Control

Comparison Operators

OperatorMeaning
==Equal to
!=Not equal to
<Less than
>Greater Than
<=Less than or Equal to
>=Greater than or Equal to

These operators evaluate to True or False depending on the values you give them.

Examples:

>>> 42 == 42
True
>>> 40 == 42
False
>>> 'hello' == 'hello'
True
>>> 'hello' == 'Hello'
False
>>> 'dog' != 'cat'
True
>>> 42 == 42.0
True
>>> 42 == '42'
False

Boolean evaluation

Never use == or != operator to evaluate the boolean operation. Use the is or is not operators, or use implicit boolean evaluation.

NO (even if they are valid Python):

>>> True == True
True
>>> True != False
True

YES (even if they are valid Python):

>>> True is True
True
>>> True is not False
True

These statements are equivalent:

>>> if a is True:
>>>    pass
>>> if a is not False:
>>>    pass
>>> if a:
>>>    pass

And these as well:

>>> if a is False:
>>>    pass
>>> if a is not True:
>>>    pass
>>> if not a:
>>>    pass

Boolean Operators

There are three Boolean operators: and, or, and not.

The and Operator’s Truth Table:

ExpressionEvaluates to
True and TrueTrue
True and FalseFalse
False and TrueFalse
False and FalseFalse

The or Operator’s Truth Table:

ExpressionEvaluates to
True or TrueTrue
True or FalseTrue
False or TrueTrue
False or FalseFalse

The not Operator’s Truth Table:

ExpressionEvaluates to
not TrueFalse
not FalseTrue

Mixing Boolean and Comparison Operators

>>> (4 < 5) and (5 < 6)
True
>>> (4 < 5) and (9 < 6)
False
>>> (1 == 2) or (2 == 2)
True

You can also use multiple Boolean operators in an expression, along with the comparison operators:

>>> 2 + 2 == 4 and not 2 + 2 == 5 and 2 * 2 == 2 + 2
True

if Statements

if name == 'Alice':
    print('Hi, Alice.')

else Statements

name = 'Bob'
if name == 'Alice':
    print('Hi, Alice.')
else:
    print('Hello, stranger.')

elif Statements

name = 'Bob'
age = 5
if name == 'Alice':
    print('Hi, Alice.')
elif age < 12:
    print('You are not Alice, kiddo.')
name = 'Bob'
age = 30
if name == 'Alice':
    print('Hi, Alice.')
elif age < 12:
    print('You are not Alice, kiddo.')
else:
    print('You are neither Alice nor a little kid.')

while Loop Statements

spam = 0
while spam < 5:
    print('Hello, world.')
    spam = spam + 1

break Statements

If the execution reaches a break statement, it immediately exits the while loop’s clause:

while True:
    print('Please type your name.')
    name = input()
    if name == 'your name':
        break
print('Thank you!')

continue Statements

When the program execution reaches a continue statement, the program execution immediately jumps back to the start of the loop.

while True:
    print('Who are you?')
    name = input()
    if name != 'Joe':
        continue
    print('Hello, Joe. What is the password? (It is a fish.)')
    password = input()
    if password == 'swordfish':
        break
print('Access granted.')

for Loops and the range() Function

>>> print('My name is')
>>> for i in range(5):
>>>     print('Jimmy Five Times ({})'.format(str(i)))
My name is
Jimmy Five Times (0)
Jimmy Five Times (1)
Jimmy Five Times (2)
Jimmy Five Times (3)
Jimmy Five Times (4)

The range() function can also be called with three arguments. The first two arguments will be the start and stop values, and the third will be the step argument. The step is the amount that the variable is increased by after each iteration.

>>> for i in range(0, 10, 2):
>>>    print(i)
0
2
4
6
8

You can even use a negative number for the step argument to make the for loop count down instead of up.

>>> for i in range(5, -1, -1):
>>>     print(i)
5
4
3
2
1
0

For else statement

This allows to specify a statement to execute in case of the full loop has been executed. Only useful when a break the condition can occur in the loop:

>>> for i in [1, 2, 3, 4, 5]:
>>>    if i == 3:
>>>        break
>>> else:
>>>    print("only executed when no item of the list is equal to 3")

Importing Modules

import random
for i in range(5):
    print(random.randint(1, 10))
import random, sys, os, math
from random import *

Ending a Program Early with sys.exit()

import sys

while True:
    print('Type exit to exit.')
    response = input()
    if response == 'exit':
        sys.exit()
    print('You typed {}.'.format(response))

Lists

A-List in Python represents a list of comma-separated values of any data type between square brackets.

var_name = [element1, element2, ...]

index method

Returns the index of the first element with the specified value

list.index(element)

append method

Adds an element at the end of the list

list.append(element)

extend method

Add the elements of a given list (or any iterable) to the end of the current list

list.extend(iterable)

insert method

Adds an element at the specified position

list.insert(position, element)

pop method

Removes the element at the specified position and returns it

list.pop(position)

remove method

The remove() method removes the first occurrence of a given item from the list

list.remove(element)

clear method

Removes all the elements from the list

list.clear()

count method

Returns the number of elements with the specified value

list.count(value)

reverse method

Reverses the order of the list

list.reverse()

sort method

Sorts the list

list.sort(reverse=True|False)
numbers = [1, 2, 3, 4, 5]
numbers[0] # returns the first item
numbers[1] # returns the second item
numbers[-1] # returns the first item from the end
numbers[-2] # returns the second item from the end
numbers.append(6) # adds 6 to the end
numbers.insert(0, 6) # adds 6 at index position of 0
numbers.remove(6) # removes 6
numbers.pop() # removes the last item
numbers.clear() # removes all the items
numbers.index(8) # returns the index of first occurrence of 8
numbers.sort() # sorts the list
numbers.reverse() # reverses the list
numbers.copy() # returns a copy of the list

Tuples

Tuples are represented as comma-separated-values of any data type within parentheses.

Tuple Creation

variable_name = (element1, element2, ...)

Let’s talk about some of the tuple methods:

count method

It returns the number of times a specified value occurs in a tuple

tuple.count(value)

index method

It searches the tuple for a specified value and returns the position.

tuple.index(value)

Sets

A set is a collection of multiple values which is both unordered and unindexed. It is written in curly brackets.

Set Creation: Way 1

var_name = {element1, element2, ...}

Set Creation: Way 2

var_name = set([element1, element2, ...])

Set Methods

Let’s talk about some of the methods of sets:

add() method

Adds an element to a set

set.add(element)

clear() method

Remove all elements from a set

set.clear()

discard() method

Removes the specified item from the set

set.discard(value)

intersection() method

Returns intersection of two or more sets

set.intersection(set1, set2 ... etc)

issubset() method

Checks if a set is a subset of another set

set.issubset(set)

pop() method

Removes an element from the set

set.pop()

remove() method

Removes the specified element from the set

set.remove(item)

union() method

Returns the union of two or more sets

set.union(set1, set2...)

Dictionaries

The dictionary is an unordered set of comma-separated key: value pairs, within {}, with the requirement that within a dictionary, no two keys can be the same.

Dictionary

<dictionary-name> = {<key>: value, <key>: value ...}

Adding Elements to a dictionary

By this method, one can add new elements to the dictionary

<dictionary>[<key>] = <value>

Updating Elements in a dictionary

If a specified key already exists, then its value will get updated

<dictionary>[<key>] = <value>

Deleting an element from a dictionary

del keyword is used to delete a specified key: value pair from the dictionary as follows:

del []

Dictionary Functions & Methods

Below are some of the methods of dictionaries

len() method

It returns the length of the dictionary, i.e., the count of elements (key: value pairs) in the dictionary

len(dictionary)

clear() method

Removes all the elements from the dictionary

dictionary.clear()

get() method

Returns the value of the specified key

dictionary.get(keyname)

items() method

Returns a list containing a tuple for each key-value pair

dictionary.items()

keys() method

Returns a list containing the dictionary’s keys

dictionary.keys()

values() method

Returns a list of all the values in the dictionary

dictionary.values()

update() method

Updates the dictionary with the specified key-value pairs

dictionary.update(iterable)

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