[Tutor] help with user input

[Marc Tompkins]

On Mon, Mar 21, 2011 at 1:12 PM, Donald Bedsole <drbedsole at gmail.com> wrote:

>
> This works fine as long as the user enters a number.  However, if they
> enter anything else, they just get the first :else statement, "You
> were too greedy."
>
> I think that's because you're trying to do a string comparison, rather than
a numeric comparison. (if next <= "50":)  You need to convert 'next' to an
int FIRST, then compare to 50, not "50".


> My googling found solutions using an exception, but that hasn't been
> introduced yet in the tutorial.  How would you solve this without
> using an exception?
>
>
If you don't want to use an exception, check the entered value first (note:
I haven't checked my code, so caveat lector) -

next = raw_input(">")
> if next.isdigit():
>     if int(next) < 50:
>         print "Nice, you're not greedy, you win!"
>     else:
>         dead("You were too greedy.")
> else:
>     dead("Man, learn to type a number!")
>

isdigit() returns True if every character is a digit; False otherwise.
http://docs.python.org/library/stdtypes.html


Using an exception:

next = raw_input(">")
> try:
>     if int(next) < 50:
>         print "Nice, you're not greedy, you win!"
>     else:
>         dead("You were too greedy.")
> except ValueError:
>     dead("Man, learn to type a number!")
>

Note that I specified ValueError - you want to make your exception handling
as specific as possible, so that if really unforeseen things go wrong, your
program doesn't blindly treat them as normal.  In other words, if any
exception other than ValueError were to pop up here, you would want the
program to terminate and show you a traceback so you could fix it.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/tutor/attachments/20110321/7658270d/attachment.html>