My solution for the December 1, 2018 Advent of Code question #2

advent2018_2.py

#!/usr/bin/env python

import itertools
import pathlib


value = 0
seen = set()
for line in itertools.cycle(
    int(line) for line in pathlib.Path("input/1.txt").read_text().splitlines()
):
    value += line
    if value in seen:
        print(f"Saw {value} twice.")
        break
    seen.add(value)