igraph/igraph — pull request #633 by ostrowr (2014-06-19 23:45:48+00:00)
Title: Python: optimal_count now returns consistently

Previously, `optimal_count` returned `None` when it had not previously been calculated, but `self._optimal_count` when it had already been set. This causes `VertexDendrogram.as_clustering()` to fail when `optimal_count` has not been called and no hint has been provided.