Python Comments

Python ignores everything after a # on a line. There's no block-comment syntax; for multi-line comments most code uses a triple-quoted string.

Single line

# Calculate the discount percentage
discount = price * 0.10
total = price - discount   # apply it

"Block" comment

"""
This module loads orders from CSV
and uploads them to the warehouse API.
Owner: @ada
"""

def upload(): ...

Docstrings

A triple-quoted string as the first statement of a module, function, class, or method becomes its docstring — readable from help(obj) and tools like Sphinx:

def discount(price: float, pct: float) -> float:
    """Return `price` reduced by `pct` percent."""
    return price * (1 - pct / 100)

help(discount)

Comments that earn their place

• Why, not what — the code already shows what.
• Non-obvious algorithms, business rules, workarounds.
• "TODO:" / "FIXME:" markers — most editors highlight them.

Example

# This is a single-line comment
"""
This is a
multi-line docstring used as a block comment.
"""
print('after comments')

Exercise

Test yourself