def diff_move(self,v,new_comm):
return _c_louvain._MutableVertexPartition_diff_move(self._partition, v, new_comm)<EOL>
Calculate the difference in the quality function if node ``v`` is
        moved to community ``new_comm``.

        Parameters
        ----------
        v
          The node to move.

        new_comm
          The community to move to.

        Returns
        -------
        float
          Difference in quality function.

        Notes
        -----
        The difference returned by diff_move should be equivalent to first
        determining the quality of the partition, then calling move_node, and then
        determining again the quality of the partition and looking at the
        difference. In other words

        >>> partition = louvain.find_partition(ig.Graph.Famous('Zachary'),
        ...                            louvain.ModularityVertexPartition)
        >>> diff = partition.diff_move(v=0, new_comm=0)
        >>> q1 = partition.quality()
        >>> partition.move_node(v=0, new_comm=0)
        >>> q2 = partition.quality()
        >>> round(diff, 10) == round(q2 - q1, 10)
        True

        .. warning:: Only derived classes provide actual implementations, the base
                     class provides no implementation for this function.