Cumulative committer count data from a git repo

cumulative.py

#!/usr/bin/env python3
# git log --format="%ae,%at" | python cumulative.py

from datetime import date
import fileinput

committers = dict()

for line in fileinput.input():
    author, time = line.split(",")

    # Warning: the comparison is a string comparison, not a number comparison
    if author not in committers or committers[author] > time:
        committers[author] = time

ac = 0
print("date,count,author")
for author, time in sorted(committers.items(), key=lambda x: x[1]):
    ac = ac + 1
    d = date.fromtimestamp(int(time))
    print("%s,%s,%s" % (d, ac, author))