Python Comments

Why Use Comments in Python?

• Improves Code Readability: Comments explain the logic behind your code.
• Facilitates Collaboration: Team members can quickly understand the code with proper comments.
• Eases Debugging and Maintenance: Comments act as reminders of why a specific approach was taken.

Types of Comments in Python

Python supports the following types of comments:

1. Single-Line Comments
2. Multi-Line Comments
3. Docstring Comments

1. Single-Line Comments

Single-line comments start with the # symbol. Everything after # on that line is treated as a comment and ignored by the Python interpreter.

Syntax:

# This is a single-line comment
print("Hello, World!")  # This comment explains the print statement

Example Explanation:

• The first line is a standalone comment.
• The second line has an inline comment after the statement.

2. Multi-Line Comments

Python doesn’t have a specific syntax for multi-line comments like other programming languages. Instead, you can use multiple single-line comments or triple quotes (” ” ” or ‘ ‘ ‘) for documentation-like comments.

Option 1: Multiple Single-Line Comments

# This is the first line of the comment
# This is the second line
print("Using multiple single-line comments")

Option 2: Triple Quotes

"""
This is a multi-line comment.
It spans multiple lines
and explains the code in detail.
"""
print("Using triple quotes for multi-line comments")

Important Note: Triple quotes are technically treated as string literals if not assigned to a variable. They are used for multi-line comments conventionally but work as documentation strings in functions or classes.

3. Docstring Comments

Docstrings, or documentation strings, are a special type of comment used to describe the purpose of a function, class or module. They are written using triple quotes and placed at the beginning of the function or class definition.

Syntax:

def greet(name):
    """
    This function greets the person
    whose name is passed as an argument.
    """
    print("Hello, " + name + "!")

How It Works:

• The triple-quoted string inside the function serves as a docstring.
• Use help() to view the docstring.

Example:

help(greet)

Output:

Help on function greet in module __main__:

greet(name)
    This function greets the person
    whose name is passed as an argument.

Best Practices for Using Comments in Python

Keep Comments Relevant: Ensure your comments add value by explaining why the code exists, not what it does.
Bad Example:

x = 10  # Assigning 10 to x

Good Example:

x = 10  # Represents the base value for calculations

Use Docstrings for Functions and Classes:
Always document the purpose of a function or class with a docstring.

Avoid Over-Commenting:
Comments should not clutter the code. Write concise, meaningful comments.

Update Comments as Code Changes:
Outdated comments can confuse readers, so keep them updated.

Use Consistent Style:
Follow a consistent commenting style across your project.

Examples of Using Comments in a Python Program

# Define a function to calculate the square of a number
def calculate_square(number):
    """
    This function calculates the square of a given number.
    It takes one argument:
    - number: The number to be squared
    """
    return number ** 2

# Use the function
result = calculate_square(5)  # Square of 5 is 25
print("Square:", result)

Explanation:

• A single-line comment explains the function declaration.
• A docstring describes the function’s purpose.
• An inline comment clarifies the result variable.

Key Differences Between Comments and Docstrings

Aspect	Comments	Docstrings
Purpose	Explain code logic	Document functions/classes
Syntax	# or triple quotes	Triple quotes
Interpreter Use	Completely ignored	Accessible via help()
Scope	Anywhere in the code	Inside functions or classes