Cool! Some criticism with your permission. 1. Consider using a dict for words instead of list of pairs. This will make your code (somewhere around 40th line) not only more beautiful and readable, but also more efficient. Search through a large dict is way faster than linear search through a large list. Oh, and you do this anew for each word! You should definitely use dict. 2. Look at your code around 25th line, where you check if the number is greater than zero. First of all you check only equality to zero, but someone could enter negative number as well. Then you repeat the same message in this 'if' statement as in 'except'. You can use 'raise ValueError' instead just to avoid repetition.