Docstrings and documentation in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a function with a docstring

What is the output of this code when calling greet('Alice')?

Python

def greet(name):
    """Return a greeting message for the given name."""
    return f"Hello, {name}!"

print(greet('Alice'))

A None

B greet

C Hello, Alice!

D Hello, name!

💡 Hint

The function returns a formatted string using the input name.

The function greet returns the string 'Hello, Alice!' when called with 'Alice'. The docstring does not affect the output.

❓ Predict Output

intermediate

Accessing a function's docstring

What will be printed by this code?

Python

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

print(add.__doc__)

A SyntaxError

B add

C None

D Add two numbers and return the result.

💡 Hint

The __doc__ attribute holds the function's docstring.

The __doc__ attribute returns the string inside the triple quotes of the function definition.

❓ Predict Output

advanced

Docstring effect on function behavior

What is the output of this code?

Python

def multiply(x, y):
    '''Multiply two numbers.'''
    result = x * y

print(multiply(3, 4))

A None

B 12

C Multiply two numbers.

D TypeError

💡 Hint

Check if the function returns a value.

The function does not return anything explicitly, so it returns None by default.

🧠 Conceptual

advanced

Purpose of docstrings in Python

Which of the following best describes the main purpose of a docstring in Python?

A To store variables inside the function.

B To document what a function, class, or module does for users and developers.

C To improve the speed of the program.

D To execute code inside the triple quotes.

💡 Hint

Docstrings are meant for explaining code, not running it.

Docstrings provide helpful explanations about code to anyone reading or using it.

❓ Predict Output

expert

Docstring and help() function output

What will be the first line printed by help(divide) for this function?

Python

def divide(a, b):
    '''Divide a by b and return the result.'''
    if b == 0:
        raise ValueError("Cannot divide by zero")
    return a / b

A Help on function divide in module __main__:

B Divide a by b and return the result.

C Traceback (most recent call last):

D None

💡 Hint

The help() function prints a header line before the docstring.

The first line printed by help() shows the function signature and location before the docstring.

Practice

1. What is the main purpose of a docstring in Python?

easy

A. To store variable values

B. To execute code automatically

C. To explain what a function, class, or module does

D. To import external libraries

Solution

1. Step 1: Understand what docstrings are

   Docstrings are special strings placed right after function, class, or module definitions to describe their purpose.

2. Step 2: Identify the purpose of docstrings

   They help explain what the code does, making it easier for others and yourself to understand.

3. Final Answer:

   To explain what a function, class, or module does -> Option C

4. Quick Check:

   Docstrings = Explanation [OK]

Hint: Docstrings describe code purpose inside triple quotes [OK]

Common Mistakes:

• Thinking docstrings run code
• Confusing docstrings with comments
• Using docstrings to store data

2. Which of the following is the correct way to write a docstring for a function in Python?

easy

A. def func():
// This is a docstring

B. def func():
# This is a docstring

C. def func():
"This is a comment"

D. def func():
'''This function does something'''

Solution

1. Step 1: Identify correct docstring syntax

   Docstrings use triple quotes (''' or """) placed immediately after the function header.

2. Step 2: Check each option

   def func(): '''This function does something''' uses triple single quotes right after the function header, which is correct. Options B and C use comments or double quotes incorrectly. def func(): // This is a docstring uses // which is not valid in Python.

3. Final Answer:

   def func(): '''This function does something''' -> Option D

4. Quick Check:

   Triple quotes after function = docstring [OK]

Hint: Docstrings use triple quotes right after function header [OK]

Common Mistakes:

• Using # instead of triple quotes
• Using single or double quotes only
• Placing docstring before function header

3. What will be the output of the following code?

def greet():
    '''Return a greeting message.'''
    return "Hello!"

print(greet.__doc__)

medium

A. Return a greeting message.

B. None

C. Hello!

D. SyntaxError

Solution

1. Step 1: Understand __doc__ attribute

   The __doc__ attribute of a function returns its docstring, which is the string inside triple quotes right after the function header.

2. Step 2: Check the function's docstring

   The function greet has the docstring 'Return a greeting message.'. So, greet.__doc__ will output this string.

3. Final Answer:

   Return a greeting message. -> Option A

4. Quick Check:

   Function.__doc__ = docstring text [OK]

Hint: Use function.__doc__ to get its docstring text [OK]

Common Mistakes:

• Expecting function return value instead of docstring
• Confusing __doc__ with print output
• Assuming __doc__ is None if no docstring

4. Identify the error in the following code snippet:

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

medium

A. Docstring should use single quotes

B. Missing closing triple quotes for the docstring

C. Incorrect indentation of return statement

D. Function missing return statement

Solution

1. Step 1: Check docstring syntax

   The docstring starts with triple double quotes """ but does not have a closing triple quote before the return statement.

2. Step 2: Identify the error caused

   Without closing triple quotes, Python treats the return line as part of the string, causing a syntax error.

3. Final Answer:

   Missing closing triple quotes for the docstring -> Option B

4. Quick Check:

   Docstrings need opening and closing triple quotes [OK]

Hint: Always close triple quotes in docstrings [OK]

Common Mistakes:

• Forgetting to close triple quotes
• Indenting return inside docstring
• Using single quotes inconsistently

5. You want to write a docstring for a function that calculates the area of a rectangle. Which of the following docstrings best follows good documentation practice?

hard

A. """Calculate the area of a rectangle given width and height.

Parameters:
width (float): The width of the rectangle.
height (float): The height of the rectangle.

Returns:
float: The area of the rectangle."""

B. """Calculate area."""

C. """Area function"""

D. """Returns width * height"""

Solution

1. Step 1: Understand good docstring content

   A good docstring clearly explains what the function does, its parameters, and what it returns.

2. Step 2: Compare options

   """Calculate the area of a rectangle given width and height. Parameters: width (float): The width of the rectangle. height (float): The height of the rectangle. Returns: float: The area of the rectangle.""" provides a clear description, lists parameters with types, and explains the return value. Other options are too short or vague.

3. Final Answer:

   """Calculate the area of a rectangle given width and height. Parameters: width (float): The width of the rectangle. height (float): The height of the rectangle. Returns: float: The area of the rectangle.""" -> Option A

4. Quick Check:

   Good docstrings = clear + parameters + return [OK]

Hint: Include purpose, parameters, and return in docstrings [OK]

Common Mistakes:

• Writing too short or vague docstrings
• Not mentioning parameters or return values
• Using incomplete sentences