datastructures.py 文件源码

def pop(self, key=None, default=_missing):
        """Removes and returns a key or index.

        :param key: The key to be popped.  If this is an integer the item at
                    that position is removed, if it's a string the value for
                    that key is.  If the key is omitted or `None` the last
                    item is removed.
        :return: an item.
        """
        if key is None:
            return self._list.pop()
        if isinstance(key, integer_types):
            return self._list.pop(key)
        try:
            rv = self[key]
            self.remove(key)
        except KeyError:
            if default is not _missing:
                return default
            raise
        return rv