Python Comments: Frequently Asked Questions (Ultimate FAQ Guide)

Previous Post
Python Comments: Single-Line and Multi-Line Commenting Explained

Introduction

Python comments are among the most essential elements of clean and maintainable code. Whether you’re a beginner learning how to document your scripts or an advanced developer shaping team-wide standards, understanding how comments work—and how to use them effectively—is crucial.

This guide answers all important questions about Python comments, grouped into clear categories for easy reading.

Category 1: Basics of Python Comments

Que – What are comments in Python?

Ans – Comments are non-executing lines in your Python code that help explain logic, reasoning, or important information for developers. Python ignores them at runtime, meaning they do not affect performance or behavior. Their purpose is purely for readability and maintainability.

Que – How do I write a single-line comment in Python?

Ans – Single-line comments start with the # symbol. Anything after # on that line is ignored.

# This is a comment
x = 10  # This is also a comment

They’re ideal for explaining short pieces of logic or leaving quick notes.

Que – Does Python support multi-line comments?

Ans – Python does not have an official multi-line comment syntax like some other languages. Instead, developers rely on block comments (multiple single-line comments) or multiline strings used as pseudo comments. However, the recommended way per PEP 8 is: use multiple # lines for multi-line commenting.

Que – What is the difference between a comment and a docstring?

Ans – The key difference is their purpose and accessibility.

• Comments are for explaining how the code works internally (implementation details). They are ignored by the interpreter and not accessible programmatically at runtime.
• Docstrings (Documentation Strings) are used to document code elements like modules, classes, and functions, explaining what they do. They are enclosed in triple quotes ("""...""" or '''...''') and are stored in the object’s __doc__ attribute, making them accessible to tools like $\text{Pydoc}$ and the built-in help() function.

Que – Are there any special comment formats in Python

Ans – Yes, Python has several special comment formats that serve specific purposes:

• Encoding declaration: # -*- coding: utf-8 -*- or # coding=utf-8 (specifies file encoding)
• Shebang line: #!/usr/bin/env python (on Unix-like systems to specify interpreter)
• Type hints: # type: (int, str) -> bool (older style of type annotations)
• MyPy comments: # type: ignore to tell type checkers to ignore a line
• Pylint directives: # pylint: disable=missing-docstring to control linting behavior
• Coverage directives: # pragma: no cover to exclude lines from coverage analysis

These special comments affect how tools and the interpreter process your code.

Category 2: Types of Python Comments

Que – What are inline comments?

Ans – Inline comments appear at the end of a line of code:

x = 5  # Set initial counter value

They should be used sparingly and only when the code is not self-explanatory.

Que – What are block comments?

Ans – Block comments are groups of single-line comments used to explain a section of code.

# Step 1: Read the file
# Step 2: Process the data
# Step 3: Output results

They are ideal for describing high-level operations.

Que – What are pseudo multi-line comments?

Ans – These use unassigned triple-quoted strings:

"""
This acts like a multi-line comment,
but technically it is just a string literal.
"""

Although sometimes used as comments, they are not recommended because they are stored as runtime string constants in some situations.

Category 3: Best Practices & Style

Que – What does PEP 8 say about writing comments?

Ans – PEP 8 recommends that comments:

• Be complete sentences
• Have the first letter capitalized (unless code)
• Explain why and not what
• Stay up-to-date with code changes
• Avoid obvious or redundant explanations

Good commenting improves code readability and maintainability.

Que – Should comments explain “what the code does”?

Ans – Preferably no—the code itself should make that clear.
Comments should explain why a decision was made, or context that code alone cannot express.

Weak comment:

x = x + 1  # adds 1 to x

Good comment:

x += 1  # Adjust offset to match zero-based indexing

Que – How long should comments be?

Ans – Comments should be concise but informative.
A good rule: one short sentence that clearly explains purpose or reasoning.

Category 4: TODO / FIXME / NOTE / HACK Tags

Que – What is a TODO comment?

Ans – A TODO indicates something that needs improvement or future work.

# TODO: Replace hardcoded paths with environment variables

Great for tracking upcoming tasks.

Que – What is a FIXME comment?

Ans – FIXME highlights known issues or bugs.

# FIXME: This fails on Python 3.12; update regex.

Use it to flag code that must be corrected.

Que – What is a HACK comment?

Ans – HACK signals a workaround that is not ideal but temporarily necessary.

# HACK: Using sleep() to wait for server startup; replace with proper health check.

It warns maintainers that the code is fragile.

Que – What is a NOTE comment?

Ans – NOTE is used to highlight important context or behavior.

# NOTE: The API rate limits to 100 requests/min.

Useful for clarifying non-obvious details.

Category 5: Comments in Large and Open-Source Projects

Que – How should comments be handled in large codebases?

Ans – Large projects benefit from:

• Consistent commenting style
• Descriptive block comments
• Clear documentation of complex logic
• Automated documentation tools
• Standardized TODO/FIXME tracking

Commenting discipline directly improves long-term maintainability.

Que – How should comments be written in open-source projects?

Ans – Open-source comments should be:

• Clear and beginner-friendly
• Respectful and professional
• Written assuming diverse contributors
• In line with community guidelines

Clear commenting helps onboard new contributors faster.

Category 6: Tools & Automation

Que – Can comments be used for generating documentation?

Ans – Not typical comments, but docstrings can be parsed by tools like:

• Sphinx
• MkDocs
• pdoc
• pydoc

Some tools use special tags (like in Django or FastAPI), but regular comments are not stored in runtime.

Que – Are there tools that help check comment quality?

Ans – Yes. Static analysis tools like:

• pylint
• flake8
• ruff

can flag poor comments, missing docstrings, or formatting issues.

Category 7: Behavior & Execution

Que – Do comments affect performance?

Ans – No. They are ignored completely by the interpreter and do not affect runtime speed or memory.

Que – Can comments be accessed during program execution?

Ans – No. Unlike docstrings, comments are not available at runtime. Python strips them during compilation.

# This comment cannot be accessed
def func():
    """This docstring can be accessed."""
    pass
print(func.__doc__)

Category 8: Common Mistakes

Que – What is a smelly comment?

Ans – A smelly comment indicates bad practices such as:

• Being outdated
• Being overly long
• Explaining obvious logic
• Repeating the code itself

Avoid them to keep code clean.

Que – What are W.E.T. comments?

Ans – WET = Write Everything Twice, meaning comments repeat what code already shows. This makes comments unnecessary and harder to maintain.

Example:

x = 10  # Set x to 10

The comment adds no value.

Que – Why should rude or sarcastic comments be avoided?

Ans – They create toxic environments and confuse other developers. Code should be professional and welcoming for collaborators—especially in open-source.

Que – Can I put comments inside data structures or expressions?

Ans – No—comments must be on their own line or at the end of a statement. You cannot break up a line of code with a comment.

Invalid:

result = (a + 
          # This adds b
          b)

Valid:

# Add b to a
result = a + b

Category 9: Advanced Concepts

Que – Can comments be used to disable code?

Ans – Yes, developers often “comment out” lines during debugging:

# print(data)

But this should be temporary, not permanent.

Que – Are comments stored in bytecode?

Ans – No. Python removes comments before compiling the script into .pyc bytecode.

Que – Can comments contain Unicode or emojis?

Ans – Yes, Python 3 supports Unicode in source files. But avoid using emojis in production code—they may break tools or formatting.

Que – Can I nest comments?

Ans – No, you can’t nest comments in the traditional sense since everything after # on a line is a comment. However, you can have # symbols within a comment without issue: # This is a # comment is perfectly valid, and the entire line after the first # is treated as a comment.

Category 10: Practical Questions

Que – When should I avoid commenting?

Ans – Avoid commenting when:

• The code already explains itself
• The comment repeats the code
• The comment becomes outdated quickly

Use clean, descriptive variable and function names instead.

Que – Should I comment every function?

Ans – Not necessarily.
Use docstrings for public functions, classes, and modules.
Use comments only when extra explanation is needed.

Que – How often should comments be updated?

Ans – Ideally whenever you update code.
Outdated comments are worse than no comments because they mislead developers.

Que – What should I do with huge legacy code that has no comments?

Ans – Add comments gradually:

• When fixing bugs
• When refactoring
• When adding new features

Prioritize sections with complex logic or frequent modifications.

Que – When should I add comments to my code?

Ans – Add comments when:

1. Explaining why you’re doing something that isn’t obvious from the code itself
2. Documenting complex algorithms or business logic that might be confusing
3. Providing context that isn’t clear from reading the code
4. Marking areas that need future work or improvements (using TODO, FIXME, etc.)
5. Warning about potential pitfalls or side effects that might not be apparent

Avoid commenting what the code does if it’s already obvious from well-written code. For example, don’t write # Increment x by 1 before x += 1. Good code should be self-explanatory, and comments should focus on the “why” rather than the “what”.

Que – What makes a good comment?

Ans – A good comment is:

• Clear and concise, avoiding unnecessary words
• Honest (don’t let comments and code diverge over time)
• Helpful to others (including your future self who might forget the context)
• Focused on the “why” rather than the “what”
• Consistent in style with the rest of the codebase

Good comments complement the code by providing information that isn’t obvious from reading the code itself. They should enhance understanding without cluttering the code.

Que – My comment is long. How should I format it?

Ans – For long comments, use the multi-line approach with #. Keep your lines to a reasonable length (often 79 or 99 characters, as per style guides like PEP 8) to avoid horizontal scrolling.

# This function uses a complex regularization technique to prevent
# overfitting in the model. The specific algorithm was chosen
# because it handles sparse data better than the alternatives.
# See JIRA ticket DATA-42 for the full discussion.

Conclusion

Python comments are powerful tools when used correctly. They can drastically improve code understanding, reduce onboarding time, and prevent confusion. Use comments to explain intent, clarify complexity, and document decisions—not to restate the obvious.

This FAQ guide covers everything from basics to advanced techniques, giving you the ultimate reference for writing clean, effective, and professional comments in Python.

Next Post
Python Docstrings: The Complete Guide (Types, Examples, Best Practices & PEP 257)

Suggested Posts
1. Python Comments: The Complete Guide (Types, PEP 8, Best Practices & Examples)
2. Python Comments: Single-Line and Multi-Line Commenting Explained