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🌱 Beginner

Python Comments – Single Line, Multi-line, and Docstrings

Comments are lines in your code that Python ignores — they exist solely for humans to read. Good comments explain the WHY behind code, document complex logic, and make codebases maintainable by teams. This lesson covers all comment types in Python and teaches you when to write them.

⏱️ 12 min read 🎯 Beginner 📅 Updated 2026

Single-Line Comments

Any text after a # symbol on a line is a comment. Python ignores everything from the # to the end of that line.

Python
# This is a full-line comment
print("Hello")  # This is an inline comment

# Multiple single-line comments:
# Step 1: Get user input
# Step 2: Validate it  
# Step 3: Process it
▶ Output
Hello

Multi-Line Comments (Triple Quotes)

Python doesn't have a dedicated multi-line comment syntax. The convention is to use triple-quoted strings (they are technically string literals that get assigned to nothing, so Python ignores them).

Python
"""
This is a multi-line
"comment" using triple quotes.
Python evaluates it as a string but discards it.
"""

print("Code continues here")
▶ Output
Code continues here
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Docstrings – Documentation Strings

Docstrings are triple-quoted strings placed as the first statement in functions, classes, or modules. Unlike regular comments, docstrings are accessible at runtime via .__doc__ and are used by documentation generators.

Python
def calculate_area(radius):
    """
    Calculate the area of a circle.

    Args:
        radius (float): The radius of the circle.

    Returns:
        float: The area of the circle.
    """
    import math
    return math.pi * radius ** 2

print(calculate_area(5))
print(calculate_area.__doc__)
▶ Output
78.53981633974483 Calculate the area of a circle. ...

When to Write Comments – Best Practices

Comments should explain WHY, not WHAT. Well-named code explains itself. Only add comments when the reasoning is not obvious.

Python
# ❌ Useless comment - the code already says this
x = x + 1  # increment x by 1

# ✅ Useful comment - explains non-obvious behavior
x = x + 1  # Offset by 1 to convert 0-based index to 1-based display

# ✅ Useful: explains a workaround
# Using int() instead of round() here because the legacy API
# expects truncated values, not rounded (see ticket #1234)
result = int(value)
💡
Tip

The best code requires no comments because variable and function names make the intent clear. Aim for self-documenting code first, comments second.

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