Day 20/100: Writing Pythonic Code – Introduction to PEP 8

Welcome to Day 20 of the 100 Days of Python series!
You’ve learned a lot of Python by now — but are you writing it the Pythonic way?

Today, we explore PEP 8, Python’s official style guide, and what it means to write “Pythonic” code — clean, readable, and professional.

Let’s dive in and make your code look (and feel) like it was written by a pro. 🐍✨

📦 What You’ll Learn

• What Pythonic code means
• What PEP 8 is and why it matters
• Key style rules from PEP 8
• Tools to auto-format your code
• Real before-and-after examples

🧠 What Is Pythonic Code?

"Pythonic" code is code that follows best practices and idioms of the Python language. It's:

• Readable
• Concise but clear
• Consistent
• Elegant

In short: code that feels natural in Python.

📜 What Is PEP 8?

PEP 8 stands for Python Enhancement Proposal #8, which provides the style guide for writing Python code.

It covers things like:

• Naming conventions
• Code layout
• Import order
• Indentation
• Line length
• Spacing

🧠 Think of PEP 8 as the grammar guide for Python code.

🧾 10 Key PEP 8 Rules (with Examples)

1. ✅ Use 4 Spaces for Indentation

# ✅ Correct
def greet():
    print("Hello")

# ❌ Incorrect (Tabs or 2 spaces)

2. ✅ Keep Lines ≤ 79 Characters

Break long lines using \ or parentheses:

print("This is a long sentence that we break into"
      " multiple lines for better readability.")

3. ✅ Leave 2 Blank Lines Between Functions

def func_one():
    pass


def func_two():
    pass

4. ✅ Add Spaces Around Operators

x = 5 + 2  # ✅
x=5+2      # ❌

5. ✅ Use Meaningful Variable Names

# ✅
user_age = 25

# ❌
ua = 25

6. ✅ Naming Conventions

7. ✅ Import One Module Per Line

import os
import sys  # ✅ Good

# import os, sys ❌ Bad

Also, group imports like this:

1. Standard library
2. Third-party packages
3. Local application imports

8. ✅ Use Docstrings for Functions

def greet(name):
    """Greet the user by name."""
    print(f"Hello, {name}")

9. ✅ Avoid Unused Variables

for i in range(5):  # ✅ if i is used
    print(i)

for _ in range(5):  # ✅ if i is not used
    print("Hi")

10. ✅ Use is/is not for None Checks

if user is None:  # ✅
    print("No user found.")

🧰 Tools to Auto-Format Code

• Black – Auto-formats your code to be PEP 8 compliant
• flake8 – Linter to show warnings and errors
• pylint – Advanced static code checker
• isort – Automatically sorts your import statements

pip install black flake8 isort

Format a file with Black:

black your_script.py

✨ Before vs After Example

❌ Unpythonic

def myfunc(x):print(x+  5)

✅ Pythonic

def my_func(x):
    print(x + 5)

🧼 Why It Matters

• ✅ Easier to read and maintain
• ✅ Collaborators understand your code faster
• ✅ Helps catch bugs early
• ✅ Shows professionalism and pride in your work
• ✅ Essential in team projects and open-source

🧠 Recap

Today you learned:

• What Pythonic code means
• What PEP 8 is and why it’s important
• 10 practical rules for writing clean Python
• Tools like Black, flake8, and isort
• How better code formatting improves quality