Docstring

Learn function documentation with """...""".

Docstring

A docstring is a triple-quoted string that describes what a function does. It goes on the first line of the body:

def add(a, b):
    """Add two numbers and return the result."""
    return a + b

The docstring can be read with help(add) or add.__doc__. It explains how to use the function and makes teamwork easier.

Docstring conventions

A good docstring describes what the function does, its parameters and return value:

def divide(a, b):
    """Divide a by b.

    Parameters:
        a: dividend
        b: divisor
    Returns:
        quotient (float)
    """
    return a / b

This gives developers a chance to use the function correctly. IDEs show the docstring as a hint.

Exercise Write a function with a docstring

Define a function called square that takes a parameter n. Put a docstring """Return the square of n.""" on the first line of the body. Return n * n. Assign square(5) to result. Then print print(result).

Show example solution

def square(n):
    """Return the square of n."""
    return n * n
result = square(5)
print(result)

Test yourself

Where is a docstring written?
- Before the function name
- After the function call
- On the first line of the function body
- After the return statement
Show answer

On the first line of the function body — A docstring goes on the first line of the body.

Complete the docstring

def add(a, b):
    ____Add two numbers."""
    return a + b

Show answer

def add(a, b):
    """Add two numbers."""
    return a + b

Match the docstring parts

"""

Triple quotes
help()

Shows docstring
__doc__

Docstring attribute
first line

Docstring location

Next lesson: Default parameters

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