Source: Signals and Noise
Part 1: Given a list of strings, find the most common character in each position.
One reason I love Python’s defaultdict
(although it’s never strictly necessary). I can make a nested map of position -> character -> count that automatically defaults to 0 without having to worry at all if I’m seeing the index/character for the first time or not.
from collections import defaultdict as ddict
counters = ddict(lambda : ddict(lambda : 0))
with open(args.input, 'r') as fin:
for line in fin:
for index, character in enumerate(line.strip()):
counters[index][character] += 1
print(''.join(
max((count, character) for character, count in counters[index].items())[1]
for index in sorted(counters)
))
Part 2: Find the least common character for each position (that occurs at least once).
Interesting. It’s the same code, except using min instead of max. In fact:
for comparator in (max, min):
print(comparator.__name__, ''.join(
comparator((count, character) for character, count in counters[index].items())[1]
for index in sorted(counters)
))
Magic.