How to Write Python Comments That Actually Help

Good Comments Explain Why

# Bad: explains what the code already says
x = x + 1   # add 1 to x

# Good: explains intent
x = x + 1   # compensate for 0-based indexing

Docstrings for Functions

def grade(score):
    """Return letter grade for 0-100 score."""
    ...

When to Delete Comments

• The code changed and the comment is now wrong.
• The comment is just a direct translation of the code.
• A good variable name makes the comment redundant.

HKDSE Marking Note

Comments are not formally awarded marks, but markers see cleaner work when you explain non-obvious decisions — and partial credit is easier to award when intent is clear.