Tim Chase wrote: > > Python beginner here and very much enjoying it. I'm looking > > for a pythonic way to find how many listmembers are also > > present in a reference list. Don't count duplicates (eg. if > > you already found a matching member in the ref list, you can't > > use the ref member anymore). > > > > Example1: > > ref=[2, 2, 4, 1, 1] > > list=[2, 3, 4, 5, 3] > > solution: 2 > > > > Example2: > > ref=[2, 2, 4, 1, 1] > > list=[2, 2, 5, 2, 4] > > solution: 3 (note that only the first two 2's count, the third > > 2 in the list should not be counted) > > It sounds like you're looking for "set" operations: (using "ell" > for clarity) > > >>> from sets import Set > >>> a = [2,2,4,1,1] > >>> b = [2,3,4,5,3] > >>> setA = Set(a) > >>> setB = Set(b) > >>> results = setA.intersection(setB) > >>> results > Set([2,4]) > >>> intersection = [x for x in results] > >>> intersection > [2,4] > > won't set remove duplicates which he wants to preserve ? He is not just looking for the 'values' that is in common, but the occurence as well, if I understand the requirement correctly.
I would just build a dict with the value as the key and occurence as the value then loop the list and lookup. -- http://mail.python.org/mailman/listinfo/python-list
