Implement 2019 day 1 with tests in Python

2019/aoc2019/__main__.py

@@ -0,0 +1,28 @@
+import argparse
+import importlib
+import sys
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('day', type=int)
+    parser.add_argument('input', type=argparse.FileType('rt'), nargs='?', default=sys.stdin)
+    parser.add_argument('-2', '--part2', action='store_true')
+
+    args = parser.parse_args()
+
+    try:
+        day = importlib.import_module(f'.day{args.day:02d}', __package__)
+
+        if args.part2:
+            function = day.part2
+        else:
+            function = day.part1
+
+        print(function(args.input))
+
+    except ImportError:
+        sys.exit(f'Invalid day: {args.day}')
+
+
+main()

2019/aoc2019/day01.py

@@ -0,0 +1,23 @@
+from typing import TextIO
+
+
+def fuel_required(weight: int) -> int:
+    return max(0, weight // 3 - 2)
+
+
+def recursive_fuel_required(weight: int) -> int:
+    total = 0
+
+    while weight > 0:
+        weight = fuel_required(weight)
+        total += weight
+
+    return total
+
+
+def part1(data: TextIO) -> int:
+    return sum(fuel_required(int(line)) for line in data)
+
+
+def part2(data: TextIO) -> int:
+    return sum(recursive_fuel_required(int(line)) for line in data)