How do I fix this python loop?

Question

outcome=input("higher or lower")

while (outcome!= 'h' or outcome!= 'l'): 
    outcome=input("enter h or l")

print("its working")

the while loop keeps going even when i write H or L

paxdiablo · Accepted Answer · 2013-09-25 08:50:55Z

6

You need and rather than or.

Let's assume the lowercase/uppercase issue is not a problem and you enter h rather than H.

Your expression will then be:

'h' != 'h' or 'h' != 'l'
\________/    \________/
   false   or    true
   \________________/
         true

Since an object cannot be two things at once, one of those inequalities must be true. Hence the entire expression must be true.

Hence you should change it to something like:

while (outcome != 'h') and (outcome != 'l'):

or:

while outcome not in ('h', 'l'):

the latter being more succinct as the number of possibilities increases:

while outcome not in ('n', 's', 'e', 'w', 'u', 'd', 'l', 'r'):

answered Sep 13, 2013 at 4:38

paxdiablo

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3 Comments

yes thank you. i should have double checked before posting. thanks again :)

Another option: while outcome not in ('h', 'l'):

I would recomment @StevenRumbalski's answer, that I think that would be more pythonic way to do it