What Are Comments and Docstring in Python (With Programs)?

Before we start learning about Comments and Docstring in Python and its concepts, we should setup our Python Integrated Development Environment (IDE) on our local machine. Read through the following articles to learn more about What is an IDE, Popular IDEs for Python and Python installation on your machine.

Table of Contents

Introduction to Comments in Python

In Python programming, comments are text written in a program that are ignored by the compiler or interpreter. Comments allow developers to explain their code, making it easier for others (or themselves) to understand the purpose and functionality of specific sections. Writing comments is a best practice to improve the readability and maintainability of your code.

What are Comments in Program

Comments in Python are lines of text in a code file that are not executed. They exist to provide descriptions or explanations about how the code works.

When Python converts code into bytecode during execution, comments are ignored by the interpreter, which means they don’t affect program functionality.

Purpose of comments

Purpose of comments is to provide description of the written code. So that, after reading the comments another user can better understand the code, purpose and related context of the code and its related functionality and test case scenarios.

The main goal of comments is to make your code more understandable to others and youself. Comments provide:

Context => Describe why a particular code was written and why this approach was taken.
Clarity => Explain complex code or logic.
Documentation => Help other developers quickly understand your code.

Best practices for write comments

When writing comments in Python, it’s essential to follow some key best practices:

Be Short but Informative – Comments should be concise yet informative. Provide only the necessary information to avoid unnecessary verbosity.
Be Precise and Clear – Avoid vague or ambiguous comments. Make sure comments directly explain the code they refer to.
Avoid Redundancy – Comments should not repeat the information already clear from the code. Instead, they should offer insights that aren’t obvious.
Relevance specific to written code – Focus on describing specific sections of the code that need explanation. Not every line requires a comment.
Language-Specific Terminology – Use language-appropriate terminology when writing comments. For Python code, use Python-specific terms.

Program to understand comments in Python

This program is to understand the different scenarios for comments in Python. Step by step, we will understand this program in more detail.

Python Program - Writing comments in Python
print("Welcome to shbytes.com")
# This is the program to explain the comments in python

'This is also a comment written in single quotes directly in script'

print("This # is not a comment, but a string")

# This comment explain the multi-line comment in python
'This is the second line of multi-line comment'
'This is the third line of multi-line comment'
print("This line is printed after the multi-line comments")

Syntax for writing comments in Python

Comments in Python starts with “#” Hash symbol
After the “#” character, Python interpreter ignores everything till end of line

Syntax for writing comments in Python
# This is the program to explain the comments in python

This line in code snippet is a comment, anything written in this line after hash, will be ignored by Python interpreter.

But # character inside a string is treated as string, not comment

Python comments - characters inside string is not a comments 
print("This # is not a comment, but a string")

“#” symbol in between the string (with double quotes or single quotes) will not create a comment.

# is more generic to write comments in Python. But sometimes comments can also be written using single quotes.

Python comments with single quote
'This is also a comment written in single quotes directly in script'

Types of comments in Python

There are three type of comments in Python:

Single line comment – Single-line comments in Python begin with a # symbol. These comments span a single line and are used to describe what the code is doing.

Python Program - Types of comments in Python
# This is the program to explain the comments in python

'This is also a comment written in single quotes directly in script'

Multi-line comments – In Python, multi-line comments are typically written as multiple single-line comments, where each line starts with “#” symbol itself.

Python Program - Multi-line comments in Python
# This comment explain the multi-line comment in python
'This is the second line of multi-line comment'
'This is the third line of multi-line comment'
print("This line is printed after the multi-line comments")

Docstring – Docstring are special type of comments, which are used to describe and write documentation for the class, function, or module. Docstrings are written using triple double quotes “””.

Docstring in Python

Docstring are documentation strings used to explain the purpose of modules, classes, and functions.
Docstring occurs as the first statement in a module, function, class, or method definition.
Docstring are written using triple double quotes “””.
Unlike regular comments, Python processes docstrings, and they can be accessed pro-grammatically using the __doc__ attribute or the help() function.

Best Practices for Writing Docstring in Python

Be Clear and Descriptive – Docstrings should precisely describe the functionality of the module, class, or function.
Include Parameters and Return Values – If applicable, explain what parameters the function takes and what it returns.
Optional but Recommended – While docstrings are optional, it’s a good practice to include them in complex codebases.

Program to understand Docstring in Python

Docstrings are particularly useful in writing self-documenting code. They also provide additional functionality, such as integration with testing frameworks like doctest.

This program is to understand the different scenarios for Docstring in Python. Step by step, we will understand this program in more detail

Python Program to understand Docstring in Python
def docstring_function(x):
    """This a python program from Shbytes
    to explain the Docstring in python.
    Here,it takes in a number x,
    returns the square of x"""
    
    return x**2

# access docstring using __doc__ method
print(docstring_function.__doc__)

print("\n---------------------------------------------------\n")
# access docstring using help() function
help(docstring_function)

Declaring Docstring

Docstring in Python are declared with “”” triple double quotes”””.
Writing docstring for function, module or class is optional, but it is a good practice to always write docstring for function, module or class.

Python Program to understand function Docstring in Python
def docstring_function(x):
    """This a python program from Shbytes
    to explain the Docstring in python.
    Here,it takes in a number x,
    returns the square of x"""
    
    return x**2

In the above code, a Docstring using triple double quotes has been defined as a first statement for the function “docstring_function”. This Docstring is providing description about that the function.

Accessing Docstring

Docstring can be accessed using __doc__ method of the object

Python command to access Docstring in Python
# access docstring using __doc__ method
print(docstring_function.__doc__)

Also, Docstring can be accessed using the help function

Python command to access Docstring in Python
# access docstring using help() function
help(docstring_function)

Docstring for Class or Module

Now, we understand about usage of Docstring, declaration of Docstring and accessing Docstring. We used Docstring with a function definition. Let’s use Docstring with a Class or Module.

Program for Docstring with Class and Module

This program is to understand the different scenarios for Docstring with Class and Module (file). Step by step, we will understand this program in more detail.

Python Program to understand Docstring with Class and Module
"""docstring for file or module - This is the docstring module"""

class Shbytes:
    """docstring for class - this is the class Shbytes"""

def __init__(self, a):
    """docstring for __init__ - This is the initialize method"""
    self.a = a

def display_values(self):
    """docstring for display_values - this method is used to display the values"""
    print(self.a)

print("\n---------------------------------------------------\n")
# access docstring at module level
print(__doc__)

print("\n---------------------------------------------------\n")
# access docstring at class level
print(Shbytes.__doc__)

print("\n---------------------------------------------------\n")
# access docstring using class object
shbytes_class_object = Shbytes()
print(shbytes_class_object.__doc__)

print("\n---------------------------------------------------\n")
# access docstring at method level
print(display_values.__doc__)

Docstring with Module

Modules are nothing but a file in which Python code is written.

Declaring Docstring with Module – In the above code, first line is Docstring for a Module

Declaring Docstring with Module
"""docstring for file or module - This is the docstring module"""

Accessing Docstring with Module – Docstring with Modules are accessed using __doc__

Accessing Docstring with Module
# access docstring at module level
print(__doc__)

Docstring with Class

Declaring Docstring with Class – Define a Class and its first statement in triple double quotes will be a Docstring.

Docstring with Class
class Shbytes:
    """docstring for class - this is the class Shbytes"""

Accessing Docstring at Class

Docstring at Class is accessed using __doc__ method with Class name.

Accessing Docstring at Class
# access docstring at class level
print(Shbytes.__doc__)

Docstring of Class can also be accessed using __doc__ method with class object.

Accessing Docstring at Class
# access docstring using class object
shbytes_class_object = Shbytes()
print(shbytes_class_object.__doc__)

Docstring with init method

Docstring can be defined with any method include “__init__” method.

Docstring with init method
def __init__(self, a):
    """docstring for __init__ - This is the initialize method"""
    self.a = a

Conclusion: Writing Effective Comments and Docstrings in Python

Understanding how to properly use comments and docstrings can significantly improve the readability and maintainability of your Python code. Following best practices ensures that your code is not only functional but also easy to understand for future collaborators or your future self.

For further Python programming concepts, you can explore Python Variables and Data Types and Python Operators to deepen your understanding of Python fundamentals.

Code snippets and programs related to Python comments and Docstring in Python, can be accessed from GitHub Repository. This GitHub repository all contains programs related to other topics in Python tutorial.

Interview Questions & Answers

Q: What is the purpose of writing a docstring for a module in Python?

Docstring for a module provides an overview of the module’s purpose and functionality. It generally describes the module’s contents, such as classes, functions, and any important details or usage examples. This module documentation is important to understand the functionality and features of the module and how to use those features. Docstring should be the top line of the Module. Docstring For example:

"""
This module provides functions for mathematical operations
such as addition, subtraction, multiplication, and division.
"""

Q: What tools can be used to generate documentation from Python docstrings?

Many tools has been developed that helps to generate documentation from Python docstrings. Some of the tools are:

Sphinx – Sphinx is a powerful tool used to convert reStructuredText like formatted docstrings into HTML, PDF, and other formats. It is very popular and widely used to create Python project documentation. Use the following command to install sphinx => pip install sphinx
pydoc – Pydoc is a Python module that automatically generates Python documentation in text or HTML format. This generated documentation can be accessed via terminal or can be serve as a web page. Following command used to generate documentation => pydoc -w module_name
Doxygen: Doxygen was originally designed for C++, but its functionality can be extended to generate Python documentation as well. This generates documentation from annotated source code.
Epydoc: Eplydoc is a tool to generate API documentation for Python modules, based on their docstrings.

Q: How docstrings can be used for testing in Python?

Docstrings can be used for testing in Python through a feature called doctests. Doctests allow to embed test cases in the docstrings of functions, classes, or modules. Python’s doctest module can run these test cases to very the functionality. Example of doctest test cases:

def add(a, b):
    """
    Add two numbers and return the result.
    Example:
    >>> add(2, 3)
    5
    >>> add(-1, 1)
    0
    """
    return a + b

if __name__ == "__main__":
    import doctest
    doctest.testmod()

Documentation and Testing Together – Docstrings and test cases together helps to maintain updated documentation with updated test cases.
Easy to Write and Understand: Doctests and test cases are easy to write and are complement of each other.

Test Your Knowledge: Practice Quiz

Quiz on Comments and Docstring in Python

Test Your Knowledge: How Well Do You Know the Comments and Docstring in Python?

1 / 5

1. What is the format for a docstring that describes a function?

Only the function name.

The same as a comment.

A single line comment.

Triple quotes followed by description.

2 / 5

2. What character is used to indicate a single-line comment in Python?

<!–

3 / 5

3. Which of the following statements is true about writing docstring comments?

They should always be written in uppercase.

All functions must have docstrings.

They should provide a brief description of parameters and return types.

They must be placed at the top of every function.

4 / 5

4. Which of the following types of documentation does Python’s built-in help function utilize?

Docstrings

Source code

Comments

Both A and B

5 / 5

5. In Python, how can you access the docstring of a function?

function.getDoc()

function.doc

function.docstring

function.documentation

Your score is