Lambda vs regular functions in Python - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of lambda with default argument

What is the output of this code?

Python

funcs = [(lambda x=i: x*2) for i in range(3)]
results = [f() for f in funcs]
print(results)

A [0, 2, 4]

B [4, 4, 4]

C [0, 0, 0]

D TypeError

💡 Hint

Think about how default arguments capture values at definition time.

Each lambda captures the current value of i as a default argument, so calling each lambda returns double its own i value.

❓ Predict Output

intermediate

Difference in output between lambda and regular function

What is the output of this code?

Python

def make_funcs():
    funcs = []
    for i in range(3):
        def f():
            return i * 2
        funcs.append(f)
    return funcs

funcs = make_funcs()
results = [f() for f in funcs]
print(results)

A [0, 2, 4]

B [4, 4, 4]

C [0, 0, 0]

D NameError

💡 Hint

Consider when the variable i is looked up inside the function.

The inner function f uses the variable i from the outer scope, which after the loop ends is 2. So all functions return 2*2=4.

🔧 Debug

advanced

Identify the error in lambda with multiple statements

Which option shows the correct way to write a lambda that returns the sum of two numbers and prints a message?

A lambda x, y: (print('Adding'), x + y)[1]

B lambda x, y: print('Adding') + (x + y)

C lambda x, y: {print('Adding'); return x + y}

D lambda x, y: x + y; print('Adding')

💡 Hint

Remember lambdas can only have expressions, not statements.

Option A uses a tuple expression to execute print and then return the sum. Other options have syntax errors or invalid syntax for lambdas.

❓ Predict Output

advanced

Output of lambda capturing loop variable without default

What is the output of this code?

Python

funcs = []
for i in range(3):
    funcs.append(lambda: i)
results = [f() for f in funcs]
print(results)

A [0, 1, 2]

B [0, 0, 0]

C [2, 2, 2]

D SyntaxError

💡 Hint

Think about when the variable i is evaluated inside the lambda.

All lambdas refer to the same variable i, which after the loop ends is 2, so all return 2.

🧠 Conceptual

expert

Why use lambda instead of regular function?

Which of these is the best reason to use a lambda function instead of a regular function?

A To create functions that can be called without parentheses

B To improve performance by compiling faster than regular functions

C To allow multiple statements inside the function body

D To define a small anonymous function inline, especially as an argument to another function

💡 Hint

Think about where lambdas are often used in Python code.

Lambdas are used for small, unnamed functions, often passed as arguments. They cannot contain multiple statements and do not improve performance.