odict.py 文件源码

def rename(self, old_key, new_key):
        """
        Rename the key for a given value, without modifying sequence order.

        For the case where new_key already exists this raise an exception,
        since if new_key exists, it is ambiguous as to what happens to the
        associated values, and the position of new_key in the sequence.

        >>> od = OrderedDict()
        >>> od['a'] = 1
        >>> od['b'] = 2
        >>> od.items()
        [('a', 1), ('b', 2)]
        >>> od.rename('b', 'c')
        >>> od.items()
        [('a', 1), ('c', 2)]
        >>> od.rename('c', 'a')
        Traceback (most recent call last):
        ValueError: New key already exists: 'a'
        >>> od.rename('d', 'b')
        Traceback (most recent call last):
        KeyError: 'd'
        """
        if new_key == old_key:
            # no-op
            return
        if new_key in self:
            raise ValueError("New key already exists: %r" % new_key)
        # rename sequence entry
        value = self[old_key] 
        old_idx = self._sequence.index(old_key)
        self._sequence[old_idx] = new_key
        # rename internal dict entry
        dict.__delitem__(self, old_key)
        dict.__setitem__(self, new_key, value)