Python Comments

1. What is a Comment?

• A part of the code that is not executed when the script runs — completely ignored
• Purpose: add descriptive text to help programmers understand the code
• Useful when:
• Others will read your code
• You return to your own code after days/weeks/months
• A section of code is complex and needs clarification

2. Types of Comments in Python

Single-Line Comment — #

• Use the pound symbol / number sign #
• Everything to the right of # on that line is a comment
• Convention: leave 1 space between # and the comment text

# This is a single-line comment

print("hello")  # This is an inline comment (2 spaces before #)

Inline comments (same line as code) → use 2 spaces before #

• You can also use # to comment out a line of code so it doesn't run:

# print("this won't run")
print("this will run")

Multi-Line Comment — """ or '''

• Use triple quotation marks (single or double) to wrap the comment
• Can span as many lines as needed
• Both """ and ''' work the same way

"""
This is a
multi-line comment
using double quotes
"""

'''
This is also a
multi-line comment
using single quotes
'''

3. When to Use (and NOT Use) Comments

Bad comment example:

print("hello world")  # prints hello world

Anyone reading code already knows what print() does — this adds no value.

Good comment principle: Only add a comment if it genuinely aids understanding.

4. Cheat Sheet

5. Key Takeaways & Recap

1. Comments are ignored at runtime — they never affect program behavior
2. # for single-line, """ or ''' for multi-line
3. Convention: 1 space after #; 2 spaces before an inline #
4. Comments should add value — avoid stating the obvious
5. Good comments explain why, not just what