List length and membership test in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code?

Consider the following Python code. What will be printed?

Python

fruits = ['apple', 'banana', 'cherry', 'date']
print(len(fruits))
print('banana' in fruits)
print('grape' in fruits)

A

4
True
False

B

3
True
False

C

4
False
True

D

3
False
True

💡 Hint

Remember, len() counts all items in the list. The 'in' keyword checks if an item exists.

The list has 4 items, so len(fruits) is 4. 'banana' is in the list, so True. 'grape' is not, so False.

❓ Predict Output

intermediate

What is the length of the list after modification?

What will be the output of the following code?

Python

numbers = [1, 2, 3, 4, 5]
numbers.append(6)
numbers.remove(2)
print(len(numbers))

A 7

B 6

C 4

D 5

💡 Hint

Appending adds one item, removing deletes one item.

Original list has 5 items. Append adds one (6), remove deletes one (2), so total remains 5.

❓ Predict Output

advanced

What does this code print?

Analyze the code and select the correct output.

Python

items = ['pen', 'pencil', 'eraser', 'pen']
print(items.count('pen'))
print('pen' in items)
print(len(items))

A

2
True
4

B

1
True
3

C

2
False
4

D

1
False
3

💡 Hint

count() returns how many times an item appears.

'pen' appears twice, so count is 2. 'pen' is in the list, so True. List length is 4.

❓ Predict Output

advanced

What error does this code raise?

What error will this code produce when run?

Python

my_list = [10, 20, 30]
print(my_list[3])

A ValueError

B KeyError

C IndexError

D TypeError

💡 Hint

List indices start at 0 and go up to length-1.

Index 3 is out of range for a list of length 3, causing IndexError.

🧠 Conceptual

expert

How many items are in the resulting list?

What is the length of the list after this code runs?

Python

a = [1, 2]
b = a
b.append(3)
print(len(a))

A 2

B 3

C 1

D Error

💡 Hint

Remember that lists are mutable and variables can reference the same list.

Both 'a' and 'b' point to the same list. Appending via 'b' changes 'a' too, so length is 3.