testing if a character in a string is an intended one

[Skaperen]

previously i had asked which was better: word[0] in ('w','x','y','z') vs word[0] in 'wxyz'. but now i have a new variation on the problem. the value for word might be an empty string so i need to change word[0] to word[:1] to avoid an exception i don't want to happen. that means i could be doing the test word[:1] in 'wxyz' with an empty string which would always give a True value for the in operation. so i can't use that one at all and apparently must use word[:1] in ('w','x','y','z') to perform a correct test. the only alternative i can imagine is word[:1] and word[:1] in 'wxyz'.

so, now, between word[:1] in ('w','x','y','z') and word[:1] and word[:1] in 'wxyz' which is the best choice? or is there something even better that i have overlooked?