Python statement uses excessive amounts of RAM

Question

This simple statement:

zip(xrange(0, 11614321), xrange(0, 11627964))

...is eating most of my RAM. (>150 MiB!) Why?

Edit: Ah, re-reading the docs, I see zip returns a list, not an iterable. Anything like zip that returns an iterable?

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The larger picture: I'm iterating over two large arrays of file data, and I'm doing things like iterating (0-end, 0-end), (0-end, 1-end), etc. I'd like to not slice the array, as it would cause excessive allocations of memory. I figured I'd just iterate over the indexes instead, but that doesn't seem to work, as per above. The whole code:

def subsequence_length(data_a, data_b, loc_a, loc_b):
    length = 0
    for i_a, i_b in zip(xrange(loc_a, len(data_a)), xrange(loc_b, len(data_b))):
        if data_a[i_a] == data_b[i_b]:
            length += 1
        else:
            break
    return length

Answer 1

Use izip from itertools