If we need to read in numbers as strings, we have to worry about how they're formatted. But we'll probably want the computer to deal with them as numbers, not as strings, and that can't happen if the string contains a comma or a period to separate the thousands place.
In this recipe, we'll write a short function that takes a number string and returns the number. The function will strip out all the extra punctuation inside the number, and only leave the last separator: hopefully the one marking the decimal place.