-                o = ord(line[i])
-                if (o >= 97 and o <= 122) or (o >= 65 and o <= 90) or \
-                   (o >= 48 and o <= 57):
+                if re.match(r"[a-zA-Z0-9]", line[i]):

Why not just use   isalnum() function here - it will be massively
faster than a regex match.