Update app.py

app.py

@@ -14,7 +14,7 @@ import matplotlib.pyplot as plt
 import math
 from datetime import datetime
 # --------- Globals --------- #
-CHARS = string.ascii_uppercase + string.digits
+CHARS = string.ascii_letters + string.digits + string.punctuation
 CHAR2IDX = {c: i + 1 for i, c in enumerate(CHARS)}
 CHAR2IDX["<BLANK>"] = 0
 BLANK_IDX = 0