[Tutor] help with user input

[Donald Bedsole]

Thank you, Marc

On Mon, Mar 21, 2011 at 4:47 PM, Marc Tompkins <marc.tompkins at gmail.com> wrote:
> 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.
>
>
>

It'll take me awhile to digest this.  Thanks for your time and your help.