Panagiotis Atmatzidis wrote:
> Hello,
>
> Can someone provide me with an error checking example about an x
> variable that needs to be number only? I used something like:
>
> def useridf():
> print ""
> print "WARNING: If you don't understand why this must be unique,
> exit and read the manual."
> print ""
> userid = input("x : ")
>
> I know that "input" accepts only numbers, but I don't want the program
> to break if someone puts other chars in it. I want to, print "Only
> numbers are accepted." which is easy. But still I can't understand how
> to do the check using if/elif/else statements.
Another way to do this is to use raw_input() to get the input as a
string, then just try to convert it to an int and catch any exception.
This also works well encapsulated into a function:
def getInt(prompt):
while 1:
s = raw_input(prompt)
try:
return int(s)
except ValueError:
print 'Only numbers are accepted'
This approach will accept negative numbers as well as positive:
>>> def getInt(prompt):
... while 1:
... s = raw_input(prompt)
... try:
... return int(s)
... except ValueError:
... print 'Only numbers are accepted'
...
>>> getInt('x: ')
x: ae
Only numbers are accepted
x: -4
-4
Kent
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