readme.md

Python Cheat Sheet

Python is a versatile and powerful programming language that is widely used for web development, data analysis, artificial intelligence, and more. Below is a detailed cheat sheet to help you get started with Python.

Basics

Comments

Single-line comments start with #.

# This is a single-line comment.

Multi-line comments can be created using triple quotes (''' or """).

"""
This is a multi-line
comment in Python.
"""

Variables and Data Types

Python is dynamically typed, so you don't need to declare the type of a variable.

# Integer
a = 5

# Float
b = 3.14

# String
c = "Hello, World!"

# List (array)
d = [1, 2, 3, 4]

# Tuple (immutable array)
e = (1, 2, 3)

# Dictionary (key-value pairs)
f = {"name": "John", "age": 30}

# Boolean
g = True

Basic Operations

Arithmetic Operators

+   # Addition
-   # Subtraction
*   # Multiplication
/   # Division
%   # Modulus (remainder)
**  # Exponentiation
//  # Floor Division

Comparison Operators

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

Control Structures

Conditional Statements

if x > y:
    print("x is greater than y")
elif x < y:
    print("x is less than y")
else:
    print("x is equal to y")

Loops

For Loop

for i in range(5):
    print(i)

While Loop

i = 0
while i < 5:
    print(i)
    i += 1

Functions

def greet(name):
    return "Hello, " + name + "!"

print(greet("John"))

Classes and Objects

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

    def bark(self):
        return self.name + " says woof!"

dog1 = Dog("Buddy")
print(dog1.bark())

File Handling

Reading a File

with open('file.txt', 'r') as file:
    content = file.read()
    print(content)

Writing to a File

with open('file.txt', 'w') as file:
    file.write("Hello, World!")

Error Handling

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")
finally:
    print("This will always execute")

Libraries and Modules

import math

print(math.sqrt(16))

Installing Libraries

You can install libraries using pip:

pip install requests

Built-in Functions

• len(): Returns the length of an object.
• type(): Returns the type of an object.
• str(), int(), float(): Type conversion functions.

Data Structures

List Comprehensions

squares = [x**2 for x in range(10)]
print(squares)

Dictionaries and Sets

Dictionaries store key-value pairs, while sets store unique elements.

# Dictionary
d = {"name": "John", "age": 30}
print(d["name"])

# Set
s = {1, 2, 3, 4, 5}
print(s)

Modules and Packages

Create a module by creating a .py file. Create a package by adding an __init__.py file.

Importing Modules

import math

print(math.sqrt(16))

Importing Functions from a Module

from math import sqrt

print(sqrt(16))

Advanced Features

Decorators

Decorators are used to modify or extend the behavior of functions.

def my_decorator(func):
    def wrapper():
        print("Something is happening before the function is called.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

say_hello()

Generators

Generators allow you to create iterators.

def my_generator():
    yield 1
    yield 2
    yield 3

for value in my_generator():
    print(value)

Context Managers

Context managers are used for resource management and cleanup.

with open('file.txt', 'r') as file:
    content = file.read()
    print(content)

This cheat sheet provides a comprehensive overview of Python syntax and features. By mastering these elements, you can effectively write robust and efficient Python code.

Happy coding!