[FIXED] Create list of zeroes/ones based on whether index is contained in a list of intervals

Issue

I have a list of lists, each indicating a numeric interval:

intervals = [[1, 4],
             [7, 9],
             [13, 18]
             ]

I need to create a list of 20 elements, where each element is 0 if its index is NOT contained in any of the intervals, and 1 otherwise. So, the desired output is:

output = [0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0]

I can think of using something simple, in the lines of:

output = zeros(20)
for index, _ in enumerate(output):
    for interval in intervals:
        if interval[0] <= index <= interval[1]:
            output[index] = 1

but is there a more efficient way?

Solution

Essentially the same as @mozway's answer, but without creating an intermediate data structure and arguably more readable:

output = np.zeros(N, dtype=int)

for start, end in intervals:
    output[np.arange(start, end+1)] = 1

Answered By - Marat