Python Sorting and Key Functions Exercises With Answers

Which call returns a new sorted list?

1. items.sort()
2. items.reverse()
3. sort(items)
4. sorted(items)correct

Answer: sorted(items)

Why: sorted returns a new list; sort changes the list in place.

What does the key argument do?

1. Selects the value used for comparisoncorrect
2. Removes duplicate values
3. Changes the list in place
4. Prints each item

Answer: Selects the value used for comparison

Why: key receives an item and returns the value Python should compare.

What does enumerate provide?

1. Only indexes
2. Indexes and valuescorrect
3. Only values
4. A sorted copy

Answer: Indexes and values

Why: Each iteration yields an index and the matching value.

What does list(zip([1, 2], ["a", "b"])) produce?

1. {'a': 1, 'b': 2}
2. [(1, 2), ('a', 'b')]
3. [(1, 'a'), (2, 'b')]correct
4. [1, 2, 'a', 'b']

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

Why: zip pairs items at the same position from each sequence.

Complete the argument that sorts from largest to smallest.

prices = [3.0, 6.0, 4.5]
print(sorted(prices, ____=True))

Answer: reverse

Why: reverse=True reverses the comparison order.

Complete the small anonymous function used as a key.

orders = [("latte", 4.5), ("tea", 3.0)]
print(sorted(orders, key=____ item: item[1]))

Answer: lambda

Why: lambda item: item[1] returns the second field for sorting.

Complete the function that adds indexes to the loop.

names = ["latte", "tea"]
for i, name in ____(names):
    print(i, name)

Answer: enumerate

Why: enumerate(names) yields an index and a name on each iteration.

Complete the function that pairs the two sequences.

names = ["latte", "tea"]
prices = [4.5, 3.0]
for name, price in ____(names, prices):
    print(name, price)

Answer: zip

Why: zip(names, prices) pairs each name with the price at the same position.

What is the output?

print(sorted([3, 1, 2]))

Answer: [1, 2, 3]

Why: sorted returns the values in ascending order.

What does this code print?

print(sorted(["bb", "a", "ccc"], key=len))

Answer: ['a', 'bb', 'ccc']

Why: The strings are ordered by length.

What does the program output?

print(list(enumerate(["a", "b"])))

Answer: [(0, 'a'), (1, 'b')]

Why: enumerate pairs each value with its index.

What appears on the screen?

print(max([4, 9, 2]))

Answer: 9

Why: max returns the largest value.