Functions (reusable code blocks) in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ trace

intermediate

Trace the output of a function call

What is the output of the following code when greet('Anna') is called?

Intro to Computing

def greet(name):
    message = f"Hello, {name}!"
    return message

print(greet('Anna'))

A Hello, Anna!

B Error: name not defined

C greet('Anna')

D Hello, name!

💡 Hint

Look at how the function uses the input name inside the message.

The function greet takes the input name and inserts it into the message string using an f-string. So calling greet('Anna') returns "Hello, Anna!" which is printed.

🧠 Conceptual

intermediate

Understanding function parameters and arguments

Which statement best describes the difference between a function parameter and an argument?

A A parameter is a variable in the function definition; an argument is the actual value passed when calling the function.

B A parameter is the value passed to a function; an argument is the function's output.

C A parameter and an argument are the same thing and can be used interchangeably.

D A parameter is the function's output; an argument is the function's name.

💡 Hint

Think about the function definition versus the function call.

Parameters are placeholders in the function definition that receive values. Arguments are the actual values given to the function when it is called.

❓ Comparison

advanced

Compare two function definitions

Which function definition correctly calculates the square of a number and returns it?

Intro to Computing

Option A:
def square(x):
    return x * x

Option B:
def square(x):
    print(x * x)

Option C:
def square(x):
    return x + x

Option D:
def square(x):
    return x ** 3

A Option B

B Option D

C Option A

D Option C

💡 Hint

Remember that the square of a number is the number multiplied by itself.

Option C returns the product of x times x, which is the square. Option C prints but does not return, so it cannot be used to get the value. Option C adds x to x, which is double, not square. Option C cubes the number.

❓ identification

advanced

Identify the error in the function

What error will occur when running this code?

Intro to Computing

def add_numbers(a, b):
    return a + b

result = add_numbers(5)
print(result)

A SyntaxError: invalid syntax

B TypeError: missing 1 required positional argument: 'b'

C NameError: name 'result' is not defined

D No error, output is 5

💡 Hint

Check how many arguments the function expects versus how many are given.

The function add_numbers requires two arguments, but only one (5) is provided. This causes a TypeError for missing an argument.

🚀 Application

expert

Predict the output of nested function calls

What is the output of this code?

Intro to Computing

def multiply(x, y):
    return x * y

def add_and_multiply(a, b, c):
    return multiply(a + b, c)

result = add_and_multiply(2, 3, 4)
print(result)

A 24

B 14

C Error: multiply function not defined

D 20

💡 Hint

First add a and b, then multiply the sum by c.

The function add_and_multiply adds 2 + 3 = 5, then calls multiply(5, 4) which returns 20.

Practice

1. What is the main purpose of a function in programming?

easy

A. To display output on the screen

B. To reuse a block of code multiple times

C. To store data permanently

D. To create a new variable

Solution

1. Step 1: Understand what a function does

   A function is a reusable block of code designed to perform a specific task.

2. Step 2: Identify the main purpose

   Functions help avoid repeating the same code by allowing reuse whenever needed.

3. Final Answer:

   To reuse a block of code multiple times -> Option B

4. Quick Check:

   Function purpose = reuse code [OK]

Hint: Functions help reuse code blocks easily [OK]

Common Mistakes:

• Confusing functions with variables
• Thinking functions store data permanently
• Believing functions only display output

2. Which of the following is the correct way to define a function named greet that takes no inputs?

easy

A. function greet() {}

B. function greet:

C. def greet()

D. def greet():

Solution

1. Step 1: Recognize Python function syntax

   In Python, functions are defined using the keyword def, followed by the function name and parentheses with parameters (empty if none), ending with a colon.

2. Step 2: Check each option

   def greet(): matches Python syntax. function greet() {} and function greet: use JavaScript style or incorrect syntax. def greet() misses the colon.

3. Final Answer:

   def greet(): -> Option D

4. Quick Check:

   Python function = def name(): [OK]

Hint: Python functions start with def and end with colon [OK]

Common Mistakes:

• Omitting the colon at the end
• Using JavaScript syntax in Python
• Leaving out parentheses

3. What will be the output of this code?

def add(x, y):
    return x + y

result = add(3, 4)
print(result)

medium

A. TypeError

B. 34

C. 7

D. None

Solution

1. Step 1: Understand the function call

   The function add takes two inputs x and y and returns their sum.

2. Step 2: Calculate the return value

   Calling add(3, 4) returns 3 + 4 = 7, which is stored in result. Printing result outputs 7.

3. Final Answer:

   7 -> Option C

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add numbers inside function returns their sum [OK]

Common Mistakes:

• Thinking it concatenates numbers as strings
• Expecting a TypeError due to missing return
• Assuming print shows None

4. Identify the error in this function definition:

def multiply(a, b)
    return a * b

medium

A. Missing colon after function header

B. Incorrect return statement

C. Function name is invalid

D. Parameters should be in square brackets

Solution

1. Step 1: Check function header syntax

   In Python, the function header must end with a colon (:). Here, it is missing after def multiply(a, b).

2. Step 2: Verify other parts

   The return statement and function name are correct. Parameters use parentheses, not square brackets.

3. Final Answer:

   Missing colon after function header -> Option A

4. Quick Check:

   Function header ends with : [OK]

Hint: Function headers always end with a colon in Python [OK]

Common Mistakes:

• Forgetting the colon at the end
• Using square brackets for parameters
• Misnaming the function

5. You want to create a function that returns the square of a number only if the number is positive; otherwise, it returns zero. Which function correctly implements this?

hard

A. def square_if_positive(n):
if n > 0:
return n * n
else:
return 0

B. def square_if_positive(n):
if n >= 0:
return n ** 2
else:
return n

C. def square_if_positive(n):
return n * n if n > 0 else None

D. def square_if_positive(n):
if n < 0:
return n * n
else:
return 0

Solution

1. Step 1: Understand the condition

   The function should return the square of n only if n is positive (greater than 0). Otherwise, it returns 0.

2. Step 2: Check each option

   def square_if_positive(n): if n > 0: return n * n else: return 0 correctly checks n > 0 and returns n * n, else 0. def square_if_positive(n): if n >= 0: return n ** 2 else: return n includes zero as positive and returns n if negative, which is incorrect. def square_if_positive(n): return n * n if n > 0 else None returns None instead of 0 when n is not positive. def square_if_positive(n): if n < 0: return n * n else: return 0 squares negative numbers and returns 0 otherwise, which is opposite.

3. Final Answer:

   def square_if_positive(n): if n > 0: return n * n else: return 0 -> Option A

4. Quick Check:

   Positive n squared, else zero [OK]

Hint: Check condition n > 0, return square else zero [OK]

Common Mistakes:

• Including zero as positive
• Returning None instead of zero
• Reversing the condition logic