Comments

Python · Reference cheat sheet

📋 Overview

Comments are notes for humans. The interpreter ignores them. Use them to explain why, not to narrate obvious code. Python also has docstrings for documenting modules, classes, and functions.

🔧 Core concepts

There is no dedicated multi-line comment syntax. Use multiple # lines, or a docstring at the top of a block when documenting.

💡 Examples

Line and inline comments:

# Calculate weekly pay from hourly rate
rate = 20
hours = 37.5
pay = rate * hours  # overtime not included yet
print(pay)

Docstring on a function:

def greet(name: str) -> str:
    """Return a friendly greeting for name."""
    return f"Hello, {name}!"


print(greet("Ada"))
print(greet.__doc__)

Module header:

#!/usr/bin/env python3
"""tiny_demo.py — practice script for comments and print."""

# TODO: add command-line args later
print("ready")

Temporarily disable code (prefer Git, not huge comment blocks):

# old_way = compute_v1(data)
result = compute_v2(data)

⚠️ Pitfalls

• Commented-out code rots quickly — delete it and use version control.
• Docstrings are strings, not comments; they become __doc__.
• Nesting quotes wrong inside docstrings can break the string.
• Over-commenting (i = i + 1 # add one) adds noise.

🔗 Related

• getting_started.md
• hello_world.md
• variables.md
• indentation.md