counting element occurrences in nested lists

Question

This is probably quite a straightforward question, but I can\'t find an answer elsewhere so I\'ll ask. What is the best way to find the number of times an element appears in

Answer 1

>>> from collections import defaultdict, Counter
>>> my_list = [['a', 'b', 'c', 'd'], ['a', 'b', 'z', 'd'], ['a', 'c', 'f', 'e'], ['d', 'w', 'f', 'a']]
>>> pos_count = defaultdict(Counter)
>>> for sublist in my_list:
        for i, c in enumerate(sublist):
            pos_count[c][i] += 1


>>> pos_count['a'][0]
3
>>> pos_count['b'][1]
2