Python raw_input with while isn't working properly

Question

I am trying to get a character input from the user using raw_input() and see if this is Y or N. The code that is supposed to do the job is given below:

#
# Things I have done before
#
c = ""
while c.capitalize() != "Y" or c.capitalize() != "N":
    c = raw_input("\n\n If you wish to continue, press Y (or N to terminate) ")

if c.capitalize() == "N":
    system.exit("Stopped script......check your files if necessary\n\n");
else:
    #Other things to do

At the moment, I am repeatedly getting the prompt even when I press Y or N. Don't know what's wrong with it. I tried to use input() instead of raw_input() but I think I am using an older version of python (2x) and that's why need to use raw_input.

Any help is appreciated.

this is really crazy and silly of me.....switching from one language to another is causing me a bit of a hickup...momentarily.... :( — ha9u63a7, Oct 16 '14 at 10:43
possible duplicate of [How do I test one variable against multiple values?](http://stackoverflow.com/questions/15112125/how-do-i-test-one-variable-against-multiple-values) — fredtantini, Oct 17 '14 at 11:08

score 4 · Accepted Answer · answered Oct 16 '14 at 10:36

4

There's a fault in your logic:

while c.capitalize() != "Y" or c.capitalize() != "N":

If I enter "Y", the first term is False, but the second one is True. False or True is True, and the while block is executed. Same thing if I enter "N". You have to use and:

while c.capitalize() != "Y" and c.capitalize() != "N":

answered Oct 16 '14 at 10:36

Carsten

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ya nice...real slick! – ha9u63a7 Oct 17 '14 at 16:19

score 1 · Answer 2 · answered Oct 16 '14 at 10:36

Your condition is wrong:
if c=='N', then the first part (c!=Y) is true, so you will loop (and conversely, if c=='Y', c won't be equals to 'N')

Change to

while (c.capitalize() != "Y" and c.capitalize() != "N"):

or better:

while (c.capitalize() not in ['Y','N']):

Python raw_input with while isn't working properly

2 Answers2