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()