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September 21, 2021 01:01 pm GMT

The Ultimate Python Cheatsheet

The Ultimate Python CheatSheet

Basic syntax from the python programming language

Showing Output To User
the print function is used to display or print output

print("Content that you wanna print on screen")

Taking Input From User
the input function is used to take input from the user

var1 = input("Enter your name: ")

Empty List
This method allows you to create an empty list

my_list = []

Empty Dictionary
By putting two curly braces, you can create a blank dictionary

my_dict = {}

Range Function
range function returns a sequence of numbers, eg, numbers starting from 0 to n-1 for range(0, n)


Comments are used to make the code more understandable for programmers, and they are not executed by compiler or interpreter.

Single line comment

#This is a single line comment

Multi-line comment

'''This is amulti-linecomment'''

Escape Sequence
An escape sequence is a sequence of characters; it doesn't represent itself when used inside string literal or character.

Newline Character


It adds a backslash


Single Quote
It adds a single quotation mark


It gives a tab space


It adds a backspace


Octal value
It represents the value of an octal number


Hex value
It represents the value of a hex number


Carriage Return
Carriage return or \r is a unique feature of Python. \r will just work as you have shifted your cursor to the beginning of the string or line.


Python string is a sequence of characters, and each character can be individually accessed. Using its index.

You can create Strings by enclosing text in both forms of quotes - single quotes or double-quotes.

variable_name = "String Data"

Slicing refers to obtaining a sub-string from the given string.

var_name[n : m]

String Methods isalnum() method
Returns True if all characters in the string are alphanumeric


isalpha() method
Returns True if all characters in the string are alphabet


isdecimal() method
Returns True if all characters in the string are decimals


isdigit() method
Returns True if all characters in the string are digits


islower() method
Returns True if all characters in the string are lower case


isspace() method
Returns True if all characters in the string are whitespaces


isupper() method
Returns True if all characters in the string are upper case


lower() method
Converts a string into lower case


upper() method
Converts a string into upper case


strip() method
It removes leading and trailing spaces in the string


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


var_name = [element1, element2, and so on]

List Methods index method
Returns the index of the first element with the specified value


append method
Adds an element at the end of the list


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


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


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


clear method
Removes all the elements from the list


count method
Returns the number of elements with the specified value


reverse method
Reverse the order of the list


sort method
Sorts the list


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

Tuple Creation

variable_name = (element1, element2, ...)

Tuple Methods count method
It returns the number of times a specified value occurs in a tuple


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


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: add() method
Adds an element to a set


clear() method
Remove all elements from a set


discard() method
Removes the specified item from the set


intersection() method
Returns intersection of two or more sets

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

issubset() method
Checks if a Set is Subset of Another Set


pop() method
Removes an element from the set


remove() method
Removes the specified element from the Set


union() method
Returns the union of Sets

set.union(set1, set2...)

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

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

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

Updating Element in a dictionary
If the specified key already exists, then its value will get updated

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

Deleting Element from a dictionary
del let to delete specified key: value pair from the dictionary

del <dictionary>[<key>]

Dictionary Functions & Methods len() method
It returns the length of the dictionary, i.e., the count of elements (key: value pairs) in the dictionary


clear() method
Removes all the elements from the dictionary


get() method
Returns the value of the specified key


items() method
Returns a list containing a tuple for each key-value pair


keys() method
Returns a list containing the dictionary's keys


values() method
Returns a list of all the values in the dictionary


update() method
Updates the dictionary with the specified key-value pairs


Conditional Statements
The if statements are the conditional statements in Python, and these implement selection constructs (decision constructs).

if Statement

if(conditional expression):statements

if-else Statement

if(conditional expression):statementselse:statements

if-elif Statement

if (conditional expression) :statementselif (conditional expression) :statementselse :statements

Nested if-else Statement

if (conditional expression):if (conditional expression):statementselse:statementselse:statements

Iterative Statements
An iteration statement, or loop, repeatedly executes a statement, known as the loop body, until the controlling expression is false (0).

For Loop
The for loop of Python is designed to process the items of any sequence, such as a list or a string, one by one.

for <variable> in <sequence>:statements_to_repeat

While Loop
A while loop is a conditional loop that will repeat the instructions within itself as long as a conditional remains true.

while <logical-expression> :loop-body

Break Statement
The break statement enables a program to skip over a part of the code. A break statement terminates the very loop it lies within.

for <var> in <sequence> :statement1if <condition> :breakstatement2statement_after_loop

Continue Statement
The continue statement skips the rest of the loop statements and causes the next iteration to occur.

for <var> in <sequence> :statement1if <condition> :continuestatement2statement3statement4

A function is a block of code that performs a specific task. You can pass parameters into a function. It helps us to make our code more organized and manageable.

Function Definition

def my_function(parameters):# Statements

File Handling
File handling refers to reading or writing data from files. Python provides some functions that allow us to manipulate data in the files.

open() function

var_name = open("file name", "opening mode")

close() function


Read () function
The read functions contains different methods, read(),readline() and readlines()

read() #return one big string

It returns a list of lines


It returns one line at a time


Write () function
This function writes a sequence of strings to the file.

write () #Used to write a fixed sequence of characters to a file

It is used to write a list of strings


Append () function
The append function is used to append to the file instead of overwriting it. To append to an existing file, simply open the file in append mode (a):

file = open("Hello.txt", "a")

Exception Handling
An exception is an unusual condition that results in an interruption in the flow of the program.

try and except
A basic try-catch block in python. When the try block throws an error, the control goes to the except block.

try:[Statement body block]raise Exception()except Exception as e:[Error processing block]

It is a programming approach that primarily focuses on using objects and classes. The objects can be any real-world entities.

The syntax for writing a class in python

class class_name:#Statements

class with a constructor
The syntax for writing a class with the constructor in python

class Abhiraj:# Default constructordef __init__(self) = "Abhiraj"# A method for printing data membersdef print_me(self):print(

Instantiating an object

<object-name> = <class-name>(<arguments>)

filter function
The filter function allows you to process an iterable and extract those items that satisfy a given condition

filter(function, iterable)

issubclass function
Used to find whether a class is a subclass of a given class (classinfo) or not

issubclass(class, classinfo)

Iterators and Generators
Here are some of the advanced topics of the Python programming language like iterators and generators

Used to create an iterator over an iterable

iter_list = iter(['Harry', 'Aakash', 'Rohan']) print(next(iter_list)) print(next(iter_list)) print(next(iter_list))

Used to generate values on the fly

# A simple generator functiondef my_gen():n = 1print('This is printed first')# Generator function contains yield statementsyield nn += 1print('This is printed second')yield nn += 1print('This is printed at last')yield n

Decorators are used to modifying the behavior of function or class. They are usually called before the definition of a function you want to decorate.

property Decorator (getter)

@propertydef name(self):return self.__name

setter Decorator
It is used to set the property 'name'

@name.setterdef name(self, value):self.__name=value

Deletor Decorator
It is used to delete the property 'name'

@name.deleter #property-name.deleter decoratordef name(self, value):print('Deleting..')del self.__name

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