Encapsulating conditional execution based on list membership - how do you do it?

[metaperl]

I have a series of scripts which retrieve files. None of these scripts
should continue if the file to be retrieved already exists in the
archive. Here is the code:

if f in path(self.storage.archive).files('*'):
                    print f, "exists in archive. Not continuing"
                    sys.exit()


self.storage is a class which gives me object-oriented access to the
filesystem directories that will be manipulated by the script. E.g.
self.storage.archive is a string which refers to a certain directory.
Initializing this object initializes all the members (input, archive,
output, workfiles) and makes all the correct directories.

ok, so I'm thinking of adding a method to the storage class so I can do
this:

self.storage.archive_has(f, print_msg=True) and sys.exit()

but really there is no need to hardcode which storage directory. So I'm
thinking:

self.storage.memberof('archive', f, print_msg=Tree) and sys.exit()


Is that the best solution you can think of?