testing if a list contains a sublist

Steven D'Aprano steve+comp.lang.python at pearwood.info
Tue Aug 16 04:12:18 CEST 2011


On Tue, 16 Aug 2011 09:26 am Johannes wrote:

> hi list,
> what is the best way to check if a given list (lets call it l1) is
> totally contained in a second list (l2)?

This is not the most efficient algorithm, but for short lists it should be
plenty fast enough:


def contains(alist, sublist):
    if len(sublist) == 0 or len(sublist) > len(alist):
        return False
    start = 0
    while True:
        try:
            p = alist.index(sublist[0], start)
        except ValueError:
            return False
        for i,x in enumerate(sublist):
            if alist[p+i] != x:
                start = p+1
                break
        else:  # for loop exits without break
            return True


-- 
Steven




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