What is the inverse of the numpy cumsum function?

z[1:] -= z[:-1].copy()

Short and sweet, with no slow Python loops. We take views of all but the first element (z[1:]) and all but the last (z[:-1]), and subtract elementwise. The copy makes sure we subtract the original element values instead of the values we’re computing. (On NumPy 1.13 and up, you can skip the copy call.)

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