Finding missing elements between two lists using collections module

findmissing.py

import collections

def findmissing(expectedlist, foundlist):
    """Compare two lists and output lists of items that are not included"""
    expected = collections.Counter(expectedlist)
    found = collections.Counter(foundlist)
    not_in_found = list((found - expected).elements())
    not_in_expected = list((expected - found).elements())
    return not_in_expected, not_in_found

#%% Example Usage:
expectedlist = ['1','2','3']
foundlist = ['2','3','4']

not_in_expected, not_in_found = findmissing(expectedlist, foundlist)

print not_in_found
print not_in_expected