[Tutor] I'm puzzled
zenzee at xs4all.nl
Mon Jan 23 01:18:53 CET 2006
On Sunday, 22 January 2006 at 16:07:06 -0800, bob wrote:
> At 03:46 PM 1/22/2006, Vincent Zee wrote:
> >Why will this little program crash when you enter the enter key?
> Thank you for including the "traceback" message in your 2nd post.
> Index error means you tried to reference an element of a sequence
> that is not there. a is the empty string when you just hit enter to
> the raw_input request. It therefore has no elements, so a raises
> the exception.
> To avoid this test first for len(a) > 0.
> >while True:
> > a = raw_input('number? ')
> > if a.isdigit():
> > print 'isdigit'
> > elif a == '-' and a[1:].isdigit():
> > print '- + isdigit'
> > elif a == 'q':
> > break
> > else:
> > print 'no digit'
Ah, thank you Bob for the explanation.
I understand now.
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