Method __contains__

Lib/mailbox.py:689–692

Return True if the keyed message exists, False otherwise.

(self, key)

        yield from self._toc.keys()

    def __contains__(self, key):
        """Return True if the keyed message exists, False otherwise."""
        self._lookup()
        return key in self._toc

    def __len__(self):
        """Return a count of messages in the mailbox."""