Handling of Paths with multiple extensions is currently not so easy with pathlib.  Specifically, I don't think there is an easy way to go from "foo.tar.gz" to "foo.ext", because Path.with_suffix only replaces the last suffix.

I would therefore like to suggest either

1/ add Path.replace_suffix, such that
    Path("foo.tar.gz").replace_suffix(".tar.gz", ".ext") == Path("foo.ext")
(this would also provide extension-checking capabilities, raising ValueError if the first argument is not a valid suffix of the initial path); or

2/ add a second argument to Path.with_suffix, "n_to_strip" (although perhaps with a better name), defaulting to 1, such that
    Path("foo.tar.gz").with_suffix(".ext", 0) == Path("foo.tar.gz.ext")
    Path("foo.tar.gz").with_suffix(".ext", 1) == Path("foo.tar.ext")
    Path("foo.tar.gz").with_suffix(".ext", 2) == Path("foo.ext") # set n_to_strip to len(path.suffixes) for stripping all of them.
    Path("foo.tar.gz").with_suffix(".ext", 3) raises a ValueError.

Best,
Antony