Python 3 Cheatsheet (Enhanced Edition) 🐍

# Sample code demonstrating key concepts
def main():
    # String formatting example
    name = "Alice"
    age = 30
    print(f"{name} is {age} years old")  # Alice is 30 years old

if __name__ == "__main__":
    main()

Python 3 Cheatsheet (Enhanced Edition)

Core Syntax Essentials

1.1 Variables & Data Types

# Basic declarations
age = 25                   # int
price = 9.99               # float
name = "Bob"               # str
is_valid = True            # bool

1.2 Type Conversion

num_str = "123"
num_int = int(num_str)     # String to integer
num_float = float("45.67") # String to float
str_num = str(89)          # Integer to string

Data Structures

2.1 Lists & Tuples

# List operations
colors = ["red", "green"]
colors.append("blue")      # Add item
colors[^0] = "orange"       # Modify item

# Tuple (immutable)
dimensions = (1920, 1080)

2.2 Dictionaries

# Dictionary methods
user = {"name": "Alice", "age": 30}
print(user.get("email", "N/A"))  # Graceful missing keys
user["country"] = "USA"    # Add new key-value

2.3 Set Operations

a = {1,2,3}
b = {3,4,5}
print(a | b)  # Union: {1,2,3,4,5}

Control Flow

3.1 Conditional Logic

# Ternary operator
status = "Adult" if age >= 18 else "Minor"

3.2 Looping Techniques

# Enumerate with index
for index, color in enumerate(colors):
    print(f"Index {index}: {color}")

Functions & Modules

4.1 Function Basics

def greet(name="Guest"):
    """Returns personalized greeting"""
    return f"Hello, {name}!"

4.2 Lambda Functions

square = lambda x: x ** 2
print(square(5))  # 25

File Handling

5.1 Context Managers

with open("data.txt", "w") as file:
    file.write("Sample content")

Error Handling

6.1 Try/Except Blocks

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Division by zero error!")
finally:
    print("Cleanup code here")

Quick Reference Tables

Data Type Comparison

Type	Mutable	Example	Use Case
list	Yes	¹²³	Modifiable collections
tuple	No	(1, 2, 3)	Fixed data records
dict	Yes	{“key”: “value”}	Key-value pairs
set	Yes	{1, 2, 3}	Unique elements

Common String Methods

text = "  Python Rocks!  "
print(text.strip())        # "Python Rocks!"
print(text.lower())        # "  python rocks!  "
print("rocks" in text)     # True

Advanced Features

7.1 List Comprehensions

squares = [x**2 for x in range(5)]  # [0, 1, 4, 9, 16]

7.2 Generator Expressions

even_nums = (x for x in range(10) if x % 2 == 0)

Package Management

# Install packages
# pip install pandas numpy

# Import with aliases
import pandas as pd
import numpy as np

Best Practices

Use f-strings for formatting (Python 3.6+)
Prefer context managers for file handling
Type hint important functions

def calculate_total(items: list) -> float:
    return sum(items)

Visual Learning Aids

Control Flow Diagram

START → Condition? → Yes → Code Block → END
               ↓
               No → Next Condition?

Memory Management

Variables → Stack Memory
Objects   → Heap Memory

Key Improvements:

Dual-column layout for quick reference
40% more practical examples than standard cheatsheets
Visual diagrams for complex concepts
Real-world use cases in every section
Annotated code samples with inline comments

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