The Ultimate Python Cheatsheet 2025

Python is one of the most popular and versatile programming languages in the world. Whether you're a beginner starting out or a seasoned developer looking to refresh your memory, this comprehensive Python Cheatsheet will guide you through every important concept from the basics to the most advanced techniques.

Introduction to Python

Python is a high-level, dynamically typed, interpreted programming language known for its readability and simplicity.

print("Hello, Python!")

Basic Syntax and Variables

x = 10
name = "Alice"
PI = 3.1415 

• Python is case-sensitive
• Use # for comments

Data Types

# Numbers
int_num = 5
float_num = 3.14

# Strings
s = "hello"

# Boolean
flag = True

# None
nothing = None 

Operators

# Arithmetic Operators: +, -, *, /, %, //, **
a = 10
b = 3
print("Arithmetic Operators:")
print(a + b)  # Addition: 13
print(a - b)  # Subtraction: 7
print(a * b)  # Multiplication: 30
print(a / b)  # Division: 3.333...
print(a % b)  # Modulus: 1
print(a ** b) # Exponentiation: 1000
print(a // b) # Floor Division: 3

# Assignment Operators
x = 5
print("\nAssignment Operators:")
x += 3
print(x)  # 8

x *= 2
print(x)  # 16

x -= 6
print(x)  # 10

# Comparison Operators: ==, !=, >, <, >=, <=
a = 5
b = 10
print("\nComparison Operators:")
print(a == b)  # False
print(a != b)  # True
print(a > b)   # False
print(a < b)   # True
print(a >= b)  # False
print(a <= b)  # True

# Logical Operators: and, or, not
x = 5
y = 10
print("\nLogical Operators:")
print(x > 0 and y > 0)  # True
print(x > 10 or y > 5)  # True
print(not(x > 10))      # True

# Bitwise Operators
a = 5     # Binary: 0101
b = 3     # Binary: 0011
print("\nBitwise Operators:")
print(a & b)   # 1  (AND)
print(a | b)   # 7  (OR)
print(a ^ b)   # 6  (XOR)
print(~a)      # -6 (NOT)
print(a << 1)  # 10 (Left Shift)
print(a >> 1)  # 2  (Right Shift)

# Identity Operators
a = [1, 2]
b = a
c = [1, 2]
print("\nIdentity Operators:")
print(a is b)       # True
print(a is c)       # False
print(a is not c)   # True

# Membership Operators
fruits = ['apple', 'banana', 'cherry']
print("\nMembership Operators:")
print('banana' in fruits)     # True
print('grape' not in fruits)  # True

Conditional Statements

if x > 0:
    print("Positive")
elif x == 0:
    print("Zero")
else:
    print("Negative")

Loops

# For loop
for i in range(5):
    print(i)

# While loop
while x > 0:
    x -= 1

Functions

def greet(name):
    return f"Hello, {name}"

print(greet("Bob"))

Lists, Tuples, Sets, Dictionaries

# List
fruits = ["apple", "banana"]

# Tuple
coordinates = (10.0, 20.0)

# Set
unique = {1, 2, 3}

# Dictionary
person = {"name": "Alice", "age": 25}

String Handling

s = "hello" print(s.upper())     # HELLO print(s[0:3])        # hel 

List Comprehensions

squares = [x*x for x in range(5)]

Modules and Packages

import math
from datetime import datetime

Exception Handling

try:
    x = 1 / 0 except ZeroDivisionError:
    print("Cannot divide by zero")
finally:
    print("Done")

File Handling

with open("file.txt", "r") as f:
    content = f.read()

Object-Oriented Programming

class Person:
    def __init__(self, name):
        self.name = name

    def greet(self):
        print("Hi, I'm", self.name)

p = Person("Alice")
p.greet()

Lambda, Map, Filter, Reduce

from functools import reduce

# Lambda
square = lambda x: x * x

# Map print(list(map(square, [1, 2, 3])))

# Filter print(list(filter(lambda x: x > 1, [0, 1, 2, 3])))

# Reduce print(reduce(lambda a, b: a + b, [1, 2, 3, 4]))

Decorators and Generators

# Decorator
def my_decorator(func):
    def wrapper():
        print("Before")
        func()
        print("After")
    return wrapper

@my_decorator
def say_hi():
    print("Hi!")

say_hi()

# Generator
def countdown(n):
    while n > 0:
        yield n
        n -= 1

for x in countdown(3):
    print(x)

Date and Time

from datetime import datetime
now = datetime.now()
print(now.strftime("%Y-%m-%d %H:%M:%S"))

Working with JSON and CSV

import json
import csv

# JSON
data = json.loads('{"name": "Bob"}')

# CSV
with open("data.csv") as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

Virtual Environments and pip

bash:

# Create venv
python -m venv venv

# Activate (Windows)
venv\Scripts\activate

# Install packages
pip install requests

Web Scraping

import requests
from bs4 import BeautifulSoup

url = "https://example.com"
r = requests.get(url)
soup = BeautifulSoup(r.text, 'html.parser')
print(soup.title.text)

Python for Web

Flask Example:

from flask import Flask
app = Flask(__name__)

@app.route("/")
def home():
    return "Hello from Flask!" 

Django:

bash:

pip install django
django-admin startproject mysite

Unit Testing

import unittest

class TestMath(unittest.TestCase):
    def test_add(self):
        self.assertEqual(1 + 1, 2)

unittest.main()

Popular Libraries and Tools

• NumPy: Numerical computing
• Pandas: Data analysis
• Matplotlib / Seaborn: Data visualization
• Scikit-learn: Machine Learning
• Requests: HTTP requests
• Pytest: Testing

Best Practices:

• Use virtual environments
• Follow PEP 8 coding standards
• Use docstrings for functions
• Keep code modular
• Handle exceptions properly

Final Thoughts

Whether you're preparing for interviews, learning Python for data science, or building your own applications, this Python Cheatsheet is your go-to resource. Bookmark it, share it, and revisit often as you continue your Python journey.

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• How to Use Python venv
• Working with requirements.txt in Python
• Installing Multiple Python Versions with pyenv-win