trying to match a string

[oj]

On Jul 18, 11:33 am, arnimavidyar... at gmail.com 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"