On Jul 18, 7:51 pm, Andrew Freeman <[EMAIL PROTECTED]> wrote:
> Andrew Freeman wrote:
> > oj wrote:
> >> On Jul 18, 12:10 pm, John Machin <[EMAIL PROTECTED]> wrote:
>
> >>> On Jul 18, 9:05 pm, oj <[EMAIL PROTECTED]> wrote:
>
> On Jul 18, 11:33 am, [EMAIL PROTECTED] wrote:
>
> > Hi,
> > Hi,
> > I am taking a string as an input from the user and it
> > should only
> > contain the chars:L , M or R
> > I tried the folllowing in kodos but they are still not
> > perfect:
> > [^A-K,^N-Q,^S-Z,^0-9]
> > [L][M][R]
> > [LRM]?L?[LRM]? etc but they do not exactly meet what I need.
> > For eg: LRLRLRLRLM is ok but LRLRLRNL is not as it has 'N'
> > .like that.
> > regards,
> > SZ
> > The string may or may not have all the three chars.
>
> With regular expressions, [^LRM] matches a character that isn't L, R
> or M. So:
> import re
> var = "LRLRLRLNR"
> if re.search(r'[^LRM]', var):
> print "Invalid"
>
> >>> Fails if var refers to the empty string.
>
> >> No it doesn't, it succeeds if var is an empty string. An empty string
> >> doesn't contain characters that are not L, R or M.
>
> >> The OP doesn't specify whether an empty string is valid or not. My
> >> interpretation was that an empty string would be valid.
>
> > Why not just use * instead of + like:
>
> > if re.search(r'^[^LRM]*$', var): # note: ^ outside [] is start of
> > string; $ means end of string
> > print "Invalid"
>
> > This will *only* print invalid when there is a character other than L,
> > R, or M or a empty string.
>
> Sorry, forget the beginning and ending markers, I just tried it out, it
> doesn't work.
> use this instead:
>
> if re.search(r'[^LRM]*', var):
> print "Invalid"
I was using kodos to check the regex.I should have used the IDE
instead.Thanks a lot again.
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