An alternative to Regex for Ranger's :travel and :narrow commands

not-Regex.py

class Matcher(str):
    def search(self, other):
        if not self:
            return True

        if self.startswith("^"):
            try:
                if self[1] == other[0]:
                    if Matcher.search(self[2:], other[1:]):
                        return True
            except IndexError:
                return True

        if self.endswith("$"):
            try:
                if self[-2] == other[-1]:
                    if Matcher.search(self[:-2], other[:-1]):
                        return True
            except IndexError:
                return True

        try:
            iother = iter(other)
            for letter in self:
                # Scan across iother for letter
                while True:
                    # if lowercase, don't be case sensitive
                    if letter.islower():
                        if letter == next(iother).lower():
                            break

                    else:
                        if letter == next(iother):
                            break

            # tmp_filter has ended before iother, so is contained sequentially in iother
            return True

        # iother has ended before tmp_filter, so doesn't contain all of tmp_filter sequentially
        except StopIteration:
            return False

class narrow(Command):
    """
    :narrow <string>

    Displays only the files which contain <string> in their basename.
    Unlike :filter, this command executes the selection and removes the filter
    again when run.
    """

    def execute(self):
        self.cancel() # Clean up
        if self.rest(1) == "..":
            self.fm.move(left=1)
        else:
            self.fm.move(right=1)

    def cancel(self):
        self.fm.thisdir.temporary_filter = None
        self.fm.thisdir.load_content(schedule=False)

    def quick(self):
        self.fm.thisdir.temporary_filter = Matcher(self.rest(1))
        self.fm.thisdir.load_content(schedule=False)

    def tab(self):
        if self.fm.env.cwd.files[-1] is not self.fm.env.cf:
            self.fm.move(down=1)
        else:
            # We're at the bottom, so wrap
            self.fm.move(to=0)