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When coding in Python, or any programming language, comments play an essential role in making your code more understandable, maintainable, and professional. Writing clear and effective comments helps not only others who may read your code but also your future self when you return to it after some time. Python offers a flexible and straightforward way to include comments that can help clarify your code without affecting its execution.
In this guide, we’ll explore what comments are, their types in Python, best practices, and how to use comments to make your Python code more efficient and comprehensible.
What are Comments?
Comments are lines in a code file that are not executed by the Python interpreter. They are intended for the programmer to add notes, explanations, or metadata about the code. These can range from clarifications about complex logic to simple annotations of what each function does. Comments can also help temporarily disable code during debugging without removing it.
In Python, comments are typically prefixed with a # symbol, which tells the interpreter to ignore the rest of the line.
Types of Comments in Python
Python supports two types of comments: single-line comments and multi-line (or block) comments.
1. Single-line Comments
Single-line comments are the most common type of comment. They begin with the # symbol and extend to the end of the line. Here’s an example:
Single-line comments are useful for adding brief explanations or notes about specific lines of code.
2. Multi-line Comments (Block Comments)
While Python doesn’t have a specific syntax for multi-line comments, you can use consecutive single-line comments to achieve the same result. Multi-line comments are helpful when explaining more complex logic, providing documentation, or leaving more detailed notes.
Alternatively, Python programmers often use triple-quoted strings (''' or """) to create multi-line comments. However, these are technically considered multi-line string literals and are not true comments. They are often used as docstrings (explained later), but if they aren’t assigned to a variable or used in any way, they can act like comments.
Best Practices for Writing Python Comments
To write effective comments, it’s important to follow some best practices that can help you write cleaner, more readable code.
1. Keep Comments Relevant
Comments should clarify the why, not the what. If your code is clear and self-explanatory, you don’t need to add a comment. For example, don’t comment on obvious or trivial lines of code:
Instead, focus on explaining complex logic, reasons behind decisions, or assumptions in the code.
2. Use Comments to Clarify Intent
Good comments explain the reasoning behind a particular approach, especially if the logic is not immediately obvious:
This clarifies why a specific method is chosen, which is crucial for someone maintaining the code.
3. Keep Comments Short and to the Point
Effective comments should be concise. Long, wordy comments can be as confusing as bad code. Use simple language to get your point across quickly.
4. Avoid Redundant Comments
Avoid adding comments that state the obvious or describe exactly what the code is doing when it’s easy to understand from the code itself:
Instead, use comments to provide context:
5. Use Consistent Commenting Style
Stick to a consistent style throughout your codebase. This includes deciding whether to use capital letters at the start of comments, how to punctuate, and where to place the comments in relation to code. Consistency helps with readability.
6. Update Comments When Code Changes
Code evolves, and your comments should evolve with it. An outdated comment is worse than no comment at all, as it can mislead readers. Make sure to revise comments when the code they describe is updated.
Docstrings: A Special Type of Comment
Docstrings are a special type of comment in Python that is used to document modules, functions, classes, and methods. These are enclosed in triple quotes (""" or ''') and serve as documentation for how a specific piece of code works. Unlike regular comments, docstrings can be accessed at runtime using the __doc__ attribute or by tools like help() in Python.
Here’s an example of how to use a docstring in a function:
Docstrings are typically used to describe what a function or class does, its parameters, and its return value. They’re useful for generating automatic documentation and for code maintainability.
Inline Comments
Inline comments are comments placed at the end of a line of code. These should be used sparingly and only when the code requires clarification that cannot be achieved by simply refactoring the code.
Avoid overuse of inline comments, as they can clutter the code and reduce readability.
Commenting Out Code for Debugging
Sometimes, you may want to comment out sections of code temporarily to troubleshoot or test specific features. Commenting code can help you isolate issues without permanently removing the code.
Once you’ve resolved the issue, be sure to remove or uncomment the code as necessary. Leaving commented-out code can confuse others or clutter your codebase.
Conclusion
Comments are an essential tool for writing clean, maintainable Python code. By following best practices such as keeping comments concise, explaining intent, avoiding redundancy, and updating comments when necessary, you can make your code more understandable to others (and yourself in the future). Use docstrings to provide detailed documentation for functions and classes, and remember that a well-commented codebase is a sign of thoughtful, professional development.
