Best Practices & Optimization PEP8, Code Optimization, Virtual Environments

Python Best Practices & Optimization

Write professional-grade Python code with PEP8, optimization tricks, and environment management!

1. PEP8: Python Style Guide

PEP8 is Python’s official style guide for readable, consistent code.

Key Rules

Category	Guideline	Example
Indentation	4 spaces per level (no tabs)	✅ def func():     print(...)
Line Length	Max 79 chars (72 for docstrings/comments)	❌ Avoid super-long lines
Naming	snake_case for variables/functions PascalCase for classes	user_id, DatabaseConnection
Imports	Group in this order: 1. Standard library 2. Third-party 3. Local	import os import requests from myapp import utils
Whitespace	Surround operators with spaces	✅ x = 5 + 3 ❌ x=5+3

Tools:

• flake8: Check PEP8 compliance (pip install flake8).
• Autopep8: Auto-format code (pip install autopep8).

2. Code Optimization

Readability vs. Performance: Prioritize readability first, optimize only when necessary.

Optimization Techniques

Technique	Example	Why It Matters
Use Built-in Functions	sum() vs manual loops	Faster (C-implemented)
Avoid Global Variables	Use local vars or class attributes	Global lookups are slower
List Comprehensions	[x*2 for x in range(10)]	Concise and faster than loops
Generator Expressions	(x*2 for x in range(10))	Memory-efficient for large data
Memoization	@lru_cache for recursive functions	Avoid redundant calculations
Vectorization with NumPy	Replace loops with array operations	Leverage optimized C code

Example: Optimizing a Loop

# Slow
result = []
for i in range(10000):
    result.append(i * 2)

# Faster
result = [i * 2 for i in range(10000)]

# Fastest (NumPy)
import numpy as np
result = np.arange(10000) * 2

3. Virtual Environments

Isolate project dependencies to avoid conflicts.

Using venv (Built-in)

# Create environment
python -m venv myenv

# Activate (Linux/Mac)
source myenv/bin/activate

# Activate (Windows)
myenv\Scripts\activate

# Install packages
pip install requests

# Deactivate
deactivate

Using virtualenv (Third-Party)

pip install virtualenv
virtualenv myenv
# Activation same as venv

Comparison

Tool	Pros	Cons
venv	Built-in, no setup	Limited customization
virtualenv	Faster, more features	Requires installation

4. Common Mistakes & Fixes

Mistake	Fix
Not using venv	Always isolate project dependencies.
Ignoring PEP8	Use linters/formatters (flake8, Black).
Premature optimization	Profile first (cProfile), optimize hotspots.
Circular imports	Restructure code or use local imports.

Best Practices

Write Docstrings:

def calculate_sum(numbers):
    """Return the sum of a list of numbers.
    
    Args:
        numbers (list): List of integers/floats.
    """
    return sum(numbers)

Use Type Hints:

from typing import List

def greet_all(names: List[str]) -> None:
    for name in names:
        print(f"Hello, {name}!")

Automate Testing:

• Write unit tests with pytest.
• Use GitHub Actions for CI/CD.

Profile Code:

python -m cProfile my_script.py

Cheat Sheet

PEP8 Quick Reference

• Variables: lowercase_with_underscores
• Constants: UPPERCASE_WITH_UNDERSCORES
• Classes: PascalCase
• Avoid: l, O, I as single-letter names.

Virtual Env Commands

# Export dependencies
pip freeze > requirements.txt

# Install from requirements
pip install -r requirements.txt

Key Takeaways

• ✅ PEP8: Write clean, consistent code.
• ✅ Optimize wisely: Prioritize readability, profile before optimizing.
• ✅ Virtual environments: Avoid dependency conflicts.

What’s Next?

• Explore dependency management with poetry.
• Learn async programming for I/O-bound tasks.
• Master debugging tools like pdb++ or IDE debuggers.

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