Hello, I have a list of dicts and I want to compare each dict in that list with a dict in a resulting list, add it to the result list if it's not there, and if it's there, update a counter associated with that dict. At first I wanted to use the solution described at http://stackoverflow.com/questions/1692388/python-list-of-dict-if-exists-increment-a-dict-value-if-not-append-a-new-dict but I got an error where one dict can not be used as a key to another dict. So the data structure I opted for is a list where each entry is a dict and an int: r = [[{'src': '', 'dst': '', 'cmd': ''}, 0]] The original dataset (that should be compared to the resulting dataset) is a list of dicts: d1 = {'src': '192.168.0.1', 'dst': '192.168.0.2', 'cmd': 'cmd1'} d2 = {'src': '192.168.0.1', 'dst': '192.168.0.2', 'cmd': 'cmd2'} d3 = {'src': '192.168.0.2', 'dst': '192.168.0.1', 'cmd': 'cmd1'} d4 = {'src': '192.168.0.1', 'dst': '192.168.0.2', 'cmd': 'cmd1'} o = [d1, d2, d3, d4] The result should be: r = [[{'src': '192.168.0.1', 'dst': '192.168.0.2', 'cmd': 'cmd1'}, 2], [{'src': '192.168.0.1', 'dst': '192.168.0.2', 'cmd': 'cmd2'}, 1], [{'src': '192.168.0.2', 'dst': '192.168.0.1', 'cmd': 'cmd1'}, 1]] What is the best way to accomplish this? I have a few code examples but none is really good and most is not working correctly. Thanks for any input on this! UPDATE The final code after Tamås comments is: from collections import namedtuple, defaultdict DataClass = namedtuple("DataClass", "src dst cmd") d1 = DataClass(src='192.168.0.1', dst='192.168.0.2', cmd='cmd1') d2 = DataClass(src='192.168.0.1', dst='192.168.0.2', cmd='cmd2') d3 = DataClass(src='192.168.0.2', dst='192.168.0.1', cmd='cmd1') d4 = DataClass(src='192.168.0.1', dst='192.168.0.2', cmd='cmd1') ds = d1, d2, d3, d4 r = defaultdict(int) for d in ds: r[d] += 1 print "list to compare" for d in ds: print d print "result after merge" for k, v in r.iteritems(): print("%s: %s" % (k, v))