Hi Vincent, > the program works with any input except when you just hit the enter key.
To be able to understand why is the crash, take a look at what the interpreter tells you: > File "untitled.py", line 12, in ? > elif a[0] == '-' and a[1:].isdigit(): > IndexError: string index out of range IndexError is raised whan you try to access an element in a list or string, an element that does not exist. In the case where you only press enter, what is the content of a???? How many characters? (hint, you may try to print a before any evaluation... Hope that gets you going, Hugo _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
