Question

Given a two-dimensional list, I would like to find everything that contains a sublist. I realize I can do something like:

#Psuedo-Python (not kosher)
def MatchAll(theList,toMatch):
    result=list(theList)
    for nMatch in toMatch:
        for nResult in result:
            if not nMatch in nResult:
                result.remove(nResult)
    return result

But there seems to be all kinds of bad about this. It seems very unlike the Python code I’ve seen and dealt with so far, besides I’m making changes to the list while iterating it, which I’ve read is not at all a good thing. Also, it seems horribly inefficient: while toMatch shouldn’t have a length greater then three for my purposes, the length of theList is unknown and could be quite large. Any help is greatly appreciated, and thanks in advance.

Answer 1

What I’d do is only keep sub-lists that match all the items in the “match” list.

def match_all(the_list, to_match):
    return [sublist for sublist in the_list 
                if all(item in sublist for item in to_match)]

You can speed this up by using a set:

def match_all(the_list, to_match):
    matches = set(to_match).issubset
    return [sublist for sublist in the_list if matches(sublist)]