day6.py

#!/bin/python

fish = [0] * 9

with open('day6.txt') as f:
    for timer in map(int, next(f).strip().split(',')):
        fish[timer] += 1

for days in range(256):
    nextdayfish = [0] * 9
    spawn = fish[0]
    for i in range(1, 9):
        fish[i-1] = fish[i]
    fish[8] = spawn
    fish[6] += spawn

print('Fish:',sum(fish))