How can I delete all zeros except for x of them in every run of consecutive zeros within a list?

Question

For every run of x or more consecutive zeros in a list in Python, I would like to del all zeros in the run except for x of them. If x = 0, then delete all zeros.

I was thinking of a Python function that took a list, L, and a number, x, as inputs.

For example, let L = [7, 0, 12, 0, 0, 2, 0, 0, 0, 27, 10, 0, 0, 0, 0, 8].

• If x = 0, then return L = [7, 12, 2, 27, 10, 8]
• If x = 1, then return L = [7, 0, 12, 0, 2, 0, 27, 10, 0, 8]
• If x = 2, then return L = [7, 0, 12, 0, 0, 2, 0, 0, 27, 10, 0, 0, 8]
• If x = 3, then return L = [7, 0, 12, 0, 0, 2, 0, 0, 0, 27, 10, 0, 0, 0, 8]
• If x = 4, then return L = [7, 0, 12, 0, 0, 2, 0, 0, 0, 27, 10, 0, 0, 0, 0, 8] (Same as original L)
• If x >= 5, then return original L as there are no runs of 5 or more consecutive zeros.

Any help would be sincerely appreciated.

Answer 1

This is easy to do as a generator. Wrap your call to it in a list constructor if you want a fresh list with the zero-runs removed.

def compact_zero_runs(iterable, max_zeros):
    zeros = 0
    for i in iterable:
        if i == 0:
            zeros += 1
            if zeros <= max_zeros:
                yield i
        else:
            zeros = 0
            yield i