M3) Replacing negative tuple values

A measurement tuple contains integers. zero_negatives(values) must return a tuple with the same length and order, replacing each negative value with 0 and retaining every other value. The input tuple must remain unchanged.

For values = (1, -2, 3, -4, 5), the required result is (1, 0, 3, 0, 5). Empty input must return ().

Compare the four implementations in Listing 1.

Listing 1: Four ways to construct a tuple with negative measurements replaced by zero.

(a) Alternative A.

def zero_negatives(values):
    result = []
    for value in values:
        if value < 0:
            result.append(0)
        else:
            result.append(value)
    return tuple(result)

(b) Alternative B.

def zero_negatives(values):
    result = [0] * len(values)
    for i in range(len(values)):
        if values[i] < 0:
            values[i] = 0
    return tuple(result)

(c) Alternative C.

def zero_negatives(values):
    result = []
    size = len(result)
    result = [0] * len(values)
    for i in range(size):
        if values[i] < 0:
            result[i] = 0
        else:
            result[i] = values[i]
    return tuple(result)

(d) Alternative D.

def zero_negatives(values):
    result = [0] * len(values)
    for i in range(len(values)):
        if values[i] < 0:
            result[i] = 0
    return tuple(result)

Which implementation satisfies the stated requirements?

• Listing 1 (a)
• Listing 1 (b)
• Listing 1 (c)
• Listing 1 (d)

TipHint

• len(values) returns the number of items.
• range(stop) visits integers from 0 up to, but excluding, stop: list(range(2)) is [0, 1]. list collects values into a new list, and range(0) is empty.
• result.append(value) adds one value to the end of the list and returns None; appending 6 to [4] changes it to [4, 6].
• tuple(result) creates a tuple containing the list’s items in order: tuple([4, 6]) is (4, 6).