bug in my code

[Ofnuts]

It all depends where you get saw from. If you are using a wrong encoding, bytes for accented characters could be converted to the wrong characters.

Also,

• "(argument, False)" is not a tuple, but a string
  
• "\'Argument should be a string'" is strange (why the simple quotes, and why escaping only one?)
  
• cat = cat.lower() should be done only once (in fact, there is a bug if your first letter is an uppercase... do you see why?)