python - Seeking a fast filter() with removal -


i'm trying write reasonably fast quicksort, has usage in many other applications.

the built in filter(function, iterable) function returns list of items in iterable when passed function return true, , faster traditional loop when need check 1 condition 1 list.

what looking function fast (like filter) not construct new list, but remove items takes old list. would, in application of single-pivot quicksort, allow removal of filter statement , near 2x speedup of partition routine.

is there such function built in python? numpy? what's fastest way implement if not?

for reference, here current partition code:

def partition(u):     lesser = singlequicksort(filter(lambda num: num <= u[0], u[1:]))     greater = singlequicksort(filter(lambda num: num > u[0], u[1:]))     return lesser, greater

using boolean mask:

def partition(u):     mask = u[1:] <= u[0]     return u[1:][mask], u[1:][~mask]

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