Summing list of counters in python
The sum function has the optional start argument which defaults to 0. Quoting the linked page:
sum(iterable[, start])Sums start and the items of an iterable from left to right and returns the total
Set start to (empty) Counter object to avoid the TypeError:
In [5]: sum(counter_list, Counter())Out[5]: Counter({'b': 5, 'c': 4, 'a': 1})
This version was faster in my experience. This is upper bound by O(log(n)).
def sum_counters(counter_list): ''' Recursive counter with a O(log(n)) Complexity ''' if len(counter_list) > 10: counter_0 = sum_counters(counter_list[:int(len(counter_list)/2)]) counter_1 = sum_counters(counter_list[int(len(counter_list)/2):]) return sum([counter_0, counter_1], Counter()) else: return sum(counter_list, Counter())global_counter = sum_counters(counter_list)