r"[A-z]" is not equivalent to r"[A-Za-z]"; it is equivalent to r"[A-Z[]^_`a-z]". But Python variable names cannot contain, e.g., a backtick. So the current regex is wrong.
r"[A-z]" is not equivalent to r"[A-Za-z]"; it is equivalent to r"[A-Z[]^_`a-z]". But Python variable names cannot contain, e.g., a backtick. So the current regex is wrong.