Why built-in functions are useful in Python - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of using built-in function len()

What is the output of this Python code using the built-in function len()?

Python

my_list = [10, 20, 30, 40]
print(len(my_list))

A 3

B 40

C TypeError

D 4

💡 Hint

The len() function returns the number of items in a list.

The list has 4 items, so len(my_list) returns 4.

❓ Predict Output

intermediate

Using built-in function sum() on a list

What will this code print when using the built-in function sum()?

Python

numbers = [1, 2, 3, 4, 5]
print(sum(numbers))

A 15

B 5

C TypeError

D 12345

💡 Hint

sum() adds all numbers in the list.

The sum of 1+2+3+4+5 is 15, so sum(numbers) returns 15.

❓ Predict Output

advanced

Output of sorted() with reverse=True

What is the output of this code using the built-in function sorted() with reverse=True?

Python

data = [3, 1, 4, 1, 5]
print(sorted(data, reverse=True))

A [1, 1, 3, 4, 5]

B [5, 4, 3, 1, 1]

C TypeError

D [5, 3, 4, 1, 1]

💡 Hint

sorted() returns a new list sorted in descending order when reverse=True.

The list sorted from highest to lowest is [5, 4, 3, 1, 1].

❓ Predict Output

advanced

Output of map() with a lambda function

What does this code print when using the built-in function map() with a lambda?

Python

nums = [1, 2, 3]
result = list(map(lambda x: x * 2, nums))
print(result)

A [2, 4, 6]

B [1, 2, 3]

C TypeError

D [3, 6, 9]

💡 Hint

map() applies the function to each item in the list.

Each number is multiplied by 2, so the result is [2, 4, 6].

🧠 Conceptual

expert

Why use built-in functions instead of writing your own?

Which of these is the best reason to use Python's built-in functions rather than writing your own code for common tasks?

A Built-in functions always use more memory than custom code.

B Built-in functions are harder to understand than custom code.

C Built-in functions are usually faster and tested for correctness.

D Built-in functions cannot be used with lists.

💡 Hint

Think about speed and reliability.

Built-in functions are optimized and tested by Python developers, making them faster and more reliable than most custom code.