from collections import Counter, defaultdict
 
x = [1, 1, 2, 3, 1, 3]
 
def times_so_far():
    return list(times_so_far_generator(x))
 
def times_so_far_generator(nums):
    counter = Counter()
    for num in nums:
        counter[num] += 1
        yield counter[num]
 
def times_so_far_d():
    return list(times_so_far_generator_d(x))
 
def times_so_far_generator_d(nums):
    counter = defaultdict(int)
    for num in nums:
        counter[num] += 1
        yield counter[num]
 
if __name__ == '__main__':
    import timeit
    print(timeit.timeit(times_so_far, number=100000))
    print(timeit.timeit(times_so_far_d, number=100000))

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