zip() function in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of zip with lists of different lengths

What is the output of this code?

list1 = [1, 2, 3, 4]
list2 = ['a', 'b']
result = list(zip(list1, list2))
print(result)

Python

list1 = [1, 2, 3, 4]
list2 = ['a', 'b']
result = list(zip(list1, list2))
print(result)

A [(1, 'a'), (2, 'b')]

B [(1, 'a'), (2, 'b'), (3, None), (4, None)]

C [(1, 'a'), (2, 'b'), (3, ''), (4, '')]

D [(1, 'a'), (2, 'b'), (3, 'c'), (4, 'd')]

💡 Hint

zip stops when the shortest input is exhausted.

The zip function pairs elements from each list until one list runs out. Here, list2 has only 2 elements, so zip stops after pairing two elements.

❓ Predict Output

intermediate

Using zip with unpacking operator

What is the output of this code?

pairs = [(1, 'x'), (2, 'y'), (3, 'z')]
numbers, letters = zip(*pairs)
print(numbers)
print(letters)

Python

pairs = [(1, 'x'), (2, 'y'), (3, 'z')]
numbers, letters = zip(*pairs)
print(numbers)
print(letters)

A

(1, 2, 3)
('x', 'y', 'z')

B [(1, 2, 3), ('x', 'y', 'z')]

C [(1, 'x'), (2, 'y'), (3, 'z')]

D Error: cannot unpack

💡 Hint

The * operator unpacks the list of tuples into separate arguments for zip.

Using *pairs unpacks the list into separate tuples, so zip groups first elements together and second elements together, returning two tuples.

❓ Predict Output

advanced

Output of zip with generator expressions

What is the output of this code?

gen1 = (x*x for x in range(3))
gen2 = (x+1 for x in range(5))
result = list(zip(gen1, gen2))
print(result)

Python

gen1 = (x*x for x in range(3))
gen2 = (x+1 for x in range(5))
result = list(zip(gen1, gen2))
print(result)

A Error: generators cannot be zipped

B [(0, 1), (1, 2), (4, 3), (9, 4), (16, 5)]

C [(0, 1), (1, 2), (4, 3)]

D [(0, 1), (1, 2)]

💡 Hint

zip stops when the shortest generator is exhausted.

gen1 produces 3 values (0,1,4), gen2 produces 5 values (1,2,3,4,5). zip stops after 3 pairs because gen1 ends.

❓ Predict Output

advanced

Result of zipping dictionaries

What is the output of this code?

dict1 = {'a': 1, 'b': 2}
dict2 = {'x': 10, 'y': 20, 'z': 30}
result = list(zip(dict1, dict2))
print(result)

Python

dict1 = {'a': 1, 'b': 2}
dict2 = {'x': 10, 'y': 20, 'z': 30}
result = list(zip(dict1, dict2))
print(result)

A [('a', 1), ('b', 2), ('x', 10), ('y', 20), ('z', 30)]

B [('a', 'x'), ('b', 'y')]

C [('a', 'x'), ('b', 'y'), ('c', 'z')]

D Error: cannot zip dictionaries

💡 Hint

Iterating a dictionary yields its keys.

When you zip dictionaries, it zips their keys. dict1 has keys 'a' and 'b', dict2 has keys 'x', 'y', 'z'. zip stops after shortest dict keys.

🧠 Conceptual

expert

Behavior of zip with infinite iterator

Consider this code:

import itertools
infinite = itertools.count(1)
finite = [10, 20, 30]
result = list(zip(infinite, finite))
print(result)

What is the output?

A Error: cannot zip infinite iterator

B Infinite loop, program never ends

C [(1, 10), (2, 20), (3, 30), (4, None)]

D [(1, 10), (2, 20), (3, 30)]

💡 Hint

zip stops when the shortest input is exhausted, even if the other is infinite.

zip stops after the finite list ends. The infinite iterator produces values but zip stops after 3 pairs.