Added alternative solution.

Author: r0f1

day03/alt.py

@@ -0,0 +1,16 @@
+from pathlib import Path
+import numpy as np
+
+lines = Path("input.txt").read_text().strip().split("\n")
+width = len(lines[0])
+result = []
+for dx, dy in [(3,1), (1,1), (5,1), (7,1), (1,2)]:
+    ctr = 0
+    x = 0
+    for line in lines[::dy]:
+        ctr += line[x] == '#'
+        x = (x + dx) % width
+    result.append(ctr)
+
+print(result[0])
+print(np.prod(result))