Python enumerate and zip Exercises With Answers

What does enumerate produce on each pass?

1. An index and an itemcorrect
2. Only the index
3. A copy of the list
4. Only the item

Answer: An index and an item

Why: enumerate yields a pair containing the position and the value.

What does this code print?

print(list(enumerate(["a", "b"], start=1)))

1. [(1, 'a'), (2, 'b')]correct
2. [(0, 'a'), (1, 'b')]
3. 1 a 2 b
4. ['a', 'b']

Answer: [(1, 'a'), (2, 'b')]

Why: start=1 begins the numbering at one, and list() shows each pair.

What does zip do when the lists have different lengths?

1. Stops at the shortest listcorrect
2. Raises ValueError
3. Pads with None
4. Repeats the shorter list

Answer: Stops at the shortest list

Why: zip stops as soon as one input is exhausted.

Which loop prints 1 Ada and 2 Grace?

1. for n, name in names:
2. for n in enumerate(names):
3. for n, name in enumerate(names, start=1):correct
4. for n, name in zip(names, start=1):

Answer: for n, name in enumerate(names, start=1):

Why: enumerate takes the iterable first and start as a keyword argument.

Complete the loop so each item gets an index.

items = ["a", "b"]
for i, item in ____(items):
    print(i, item)

Answer: enumerate

Why: enumerate yields the index and item together.

Complete the argument that starts numbering at one.

for n, item in enumerate(["a", "b"], ____=1):
    print(n, item)

Answer: start

Why: The keyword argument is start.

Complete the function that pairs two lists.

names = ["Ada", "Grace"]
scores = [92, 88]
pairs = list(____(names, scores))

Answer: zip

Why: zip walks two iterables in parallel.

Complete the call that produces (0, 'a') first.

print(next(____(["a"])))

Answer: enumerate

Why: next() asks enumerate for its first pair.

What does the program output?

print(list(enumerate(["x", "y"])))

Answer: [(0, 'x'), (1, 'y')]

Why: The default start is zero, and list() shows the pairs.

What appears on the screen?

print(list(zip([1, 2], ["a"])))

Answer: [(1, 'a')]

Why: zip stops when the shorter input runs out, so only one pair remains.

What is printed?

print([i for i, _ in enumerate("abc", start=2)])

Answer: [2, 3, 4]

Why: The indexes are 2, 3, and 4 even though the characters are not used.

What is the output?

print(dict(zip(["a", "b"], [1, 2])))

Answer: {'a': 1, 'b': 2}

Why: zip creates pairs, and dict turns each pair into a key and value.