Tell a raw string (r'') from a regular string ('')?

Question

I'm currently building a tool that will have to match filenames against a pattern. For convenience, I intend to provide both lazy matching (in a glob-like fashion) and regexp matching. For example, the following two snippets would eventually have the same effects:

@mylib.rule('static/*.html')
def myfunc():
    pass

@mylib.rule(r'^static/([^/]+)\.html')
def myfunc():
    pass

AFAIK r'' is only useful to the Python parser and it actually creates a standard str instance after parsing (the only difference being that it keeps the \).

Is anybody aware of a way to tell one from another?

I would hate to have to provide two alternate decorators for the same purpose or, worse, resorting manually parsing the string to determine if it's a regexp or not.

Answer 1

The term "raw string" is confusing because it sounds like it is a special type of string - when in fact, it is just a special syntax for literals that tells the compiler to do no interpretation of '\' characters in the string. Unfortunately, the term was coined to describe this compile-time behavior, but many beginners assume it carries some special runtime characteristics.

I prefer to call them "raw string literals", to emphasize that it is their definition of a string literal using a don't-interpret-backslashes syntax that is what makes them "raw". Both raw string literals and normal string literals create strings (or strs), and the resulting variables are strings like any other. The string created by a raw string literal is equivalent in every way to the same string defined non-raw-ly using escaped backslashes.