Comments

Comments are notes in source code that Python ignores during execution.

Use comments to explain intent, assumptions, and important details.

Single-Line Comments

Use #:

# This is a comment
print("Hello World")  # Inline comment

Multi-Line Explanations

Python has no dedicated multi-line comment syntax. The common style is multiple # lines:

# This block explains why we do something,
# not only what the code does.
# Keep comments concise and useful.

Triple-quoted strings (""" ... """) are strings, not real comments. They are usually used for docstrings.

Docstring Example

def greet(name):
    """Return greeting text for a name."""
    return f"Hello, {name}"

Complete Example

The following script shows how comments work alongside real code. Only the print() calls produce output:

# Print a greeting
print("Hello World")

# The line below is commented out, so it will not run
# print("This will not be printed")

print("Bob")    # prints a name
print(123)      # prints a number

Output:

Hello World
Bob
123

Good Commenting Practice

A good comment explains why the code does something, not what it does — the code already shows the what. Comments that just repeat the code add noise:

price = 20

# Bad: states the obvious
total = price * 2   # multiply price by 2

# Good: explains the reason
total = price * 2   # double charge applies on holidays
print(total)

A common convention is to mark unfinished work with # TODO: or # FIXME: so it is easy to search for later:

# TODO: handle negative input
def square_root(n):
    return n ** 0.5