list manipulation - Prevent testing Head with ReplaceAll

I have a list of strings list. I am trying to get rid of some elements that match string pattern patt:

list /. x_ /; StringMatchQ[x, patt] -> Nothing

I get the result I want but I also get an error:

StringMatchQ::strse: String or list of strings expected at position 1 in StringMatchQ[List, patt].

This happens because ReplaceAll also evaluates the condition on the Head of list. How can I get the result I want but prevent the error?

Answer

IMHO the simplest solution is to restrict the pattern on the left side of Condition, i.e. change x_ to x_String:

patt = ___ ~~ "a" ~~ ___;

{"good", "bad"} /. x_String /; StringMatchQ[x, patt] -> Sequence[]


(*  {"good"}  *)

You can instead use Replace as indicated in other answers, however:

• the optimal levelspec to target atomic elements like Strings is {-1}


• The default Heads value False is what prevents List from being pattern matched.

Please understand that Replace does not work the same as ReplaceAll, regardless of levelspec, because it uses a different traversal order. See: