Methods with return values in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this method call?

Consider the following Python code. What will be printed when result is printed?

Python

def multiply_by_two(x):
    return x * 2

result = multiply_by_two(5)
print(result)

A 25

B TypeError

C None

D 10

💡 Hint

Think about what the method returns when given 5.

The method multiplies the input by 2 and returns it. So 5 * 2 = 10.

❓ Predict Output

intermediate

What does this method return?

Look at this method. What will print(check_even(4)) output?

Python

def check_even(num):
    if num % 2 == 0:
        return True
    else:
        return False

print(check_even(4))

A False

B True

C None

D SyntaxError

💡 Hint

Check if 4 is divisible by 2.

4 is even, so the method returns True.

❓ Predict Output

advanced

What is the output of this recursive method?

What will be printed when factorial(4) is called and printed?

Python

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)

print(factorial(4))

A 24

B 10

C 0

D RecursionError

💡 Hint

Factorial of 4 is 4 * 3 * 2 * 1.

The factorial of 4 is 24 because 4 * 3 * 2 * 1 = 24.

❓ Predict Output

advanced

What is the value of result after this method call?

Given this code, what will result hold after calling combine_strings('Hi', 'There')?

Python

def combine_strings(a, b):
    return a + ' ' + b

result = combine_strings('Hi', 'There')

A 'Hi + There'

B 'HiThere'

C 'Hi There'

D TypeError

💡 Hint

Look at how the strings are joined with a space.

The method returns the two strings joined by a space, so result is 'Hi There'.

❓ Predict Output

expert

What is the output of this method with default and keyword arguments?

What will be printed when greet('Alice', greeting='Hello') is called?

Python

def greet(name, greeting='Hi'):
    return f"{greeting}, {name}!"

print(greet('Alice', greeting='Hello'))

A "Hello, Alice!"

B "Hi, Alice!"

C "Hello Alice"

D TypeError

💡 Hint

Check which greeting is used when a keyword argument is passed.

The keyword argument greeting='Hello' overrides the default 'Hi', so the output is 'Hello, Alice!'.

Practice

1. What does a method with a return statement do in Python?

easy

A. It sends a value back to where the method was called.

B. It prints a value on the screen.

C. It stops the program immediately.

D. It creates a new variable automatically.

Solution

1. Step 1: Understand the purpose of return

   The return statement sends a value back from the method to the caller.

2. Step 2: Differentiate from printing or stopping

   Printing shows output but does not send a value back; stopping ends execution.

3. Final Answer:

   It sends a value back to where the method was called. -> Option A

4. Quick Check:

   Method return = sends value back [OK]

Hint: Return sends value back, print shows it only [OK]

Common Mistakes:

• Confusing return with print
• Thinking return stops the program
• Believing return creates variables

2. Which of the following is the correct syntax for a method that returns the sum of two numbers a and b?

easy

A. def add(a, b): return a - b

B. def add(a, b): print(a + b)

C. def add(a, b): return a + b

D. def add(a, b): a + b

Solution

1. Step 1: Identify correct return usage

   The method must use return to send back the sum a + b.

2. Step 2: Check each option

   The version with return a - b returns the difference. The version with print(a + b) prints but returns None. The version with just a + b lacks return. Only def add(a, b): return a + b correctly returns the sum.

3. Final Answer:

   def add(a, b): return a + b -> Option C

4. Quick Check:

   Return sum = def add(a, b): return a + b [OK]

Hint: Return must be followed by value to send back [OK]

Common Mistakes:

• Using print instead of return
• Omitting return keyword
• Returning wrong expression

3. What is the output of this code?

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

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

medium

A. 7

B. 12

C. 34

D. None

Solution

1. Step 1: Understand the method call

   The method multiply returns the product of 3 and 4, which is 12.

2. Step 2: Print the returned value

   The variable result stores 12, so print(result) outputs 12.

3. Final Answer:

   12 -> Option B

4. Quick Check:

   3 * 4 = 12 [OK]

Hint: Multiply inputs, return result, print shows it [OK]

Common Mistakes:

• Adding instead of multiplying
• Printing None by missing return
• Confusing string concatenation with multiplication

4. Find the error in this method and choose the correct fix:

def greet(name):
    print("Hello, " + name)

message = greet("Alice")
print(message)

medium

A. Remove the argument name from the method.

B. Add print before calling greet.

C. Change message to greet in the last print.

D. Change print to return inside the method.

Solution

1. Step 1: Identify the problem with return value

   The method prints but does not return a value, so message is None.

2. Step 2: Fix by returning the greeting string

   Replace print with return to send the greeting back.

3. Final Answer:

   Change print to return inside the method. -> Option D

4. Quick Check:

   Return greeting to assign message [OK]

Hint: Use return to get value, not print [OK]

Common Mistakes:

• Expecting print to return a value
• Removing needed parameters
• Changing variable names incorrectly

5. You want to write a method that returns a dictionary with keys as numbers from 1 to n and values as their squares. Which method below correctly does this?

hard

A. def squares(n):
result = {}
for i in range(1, n+1):
result[i] = i * i
return result

B. def squares(n):
result = []
for i in range(n):
result.append(i * i)
return result

C. def squares(n):
return {i: i + i for i in range(1, n)}

D. def squares(n):
for i in range(1, n+1):
print(i * i)

Solution

1. Step 1: Understand the requirement

   The method must return a dictionary with keys 1 to n and values as squares.

2. Step 2: Check each option

   The loop building result = {}, setting result[i] = i * i for i in range(1, n+1), and returning result is correct. Returning a list fails. The comprehension {i: i + i for i in range(1, n)} uses doubles instead of squares and misses key n. Printing without returning fails.

3. Final Answer:

   def squares(n): result = {} for i in range(1, n+1): result[i] = i * i return result -> Option A

4. Quick Check:

   Return dict with squares = def squares(n): result = {} for i in range(1, n+1): result[i] = i * i return result [OK]

Hint: Return dict with keys and squares using loop [OK]

Common Mistakes:

• Returning list instead of dict
• Using wrong range limits
• Printing instead of returning