day 10, easy with itertools.groupby

part 2 scales thanks to codon

d10/run.py

@@ -0,0 +1,7 @@
+import sys
+from itertools import groupby as gb
+
+r = sys.argv[1]
+for _ in range(int(sys.argv[2])):
+    r = "".join(f'{n}{c}' for c,n in map(lambda x: (x[0],len(list(x[1]))), gb(r)))
+print(len(r))