:mod:`altgraph.GraphUtil` --- Utility functions ================================================ .. module:: altgraph.GraphUtil :synopsis: Utility functions The module :mod:`altgraph.GraphUtil` performs a number of more or less useful utility functions. .. function:: generate_random_graph(node_num, edge_num[, self_loops[, multi_edges]) Generates and returns a :class:`Graph <altgraph.Graph.Graph>` instance with *node_num* nodes randomly connected by *edge_num* edges. When *self_loops* is present and True there can be edges that point from a node to itself. When *multi_edge* is present and True there can be duplicate edges. This method raises :class:`GraphError <altgraph.GraphError` when a graph with the requested configuration cannot be created. .. function:: generate_scale_free_graph(steps, growth_num[, self_loops[, multi_edges]]) Generates and returns a :py:class:`~altgraph.Graph.Graph` instance that will have *steps*growth_n um* nodes and a scale free (powerlaw) connectivity. Starting with a fully connected graph with *growth_num* nodes at every step *growth_num* nodes are added to the graph and are connected to existing nodes with a probability proportional to the degree of these existing nodes. .. warning:: The current implementation is basically untested, although code inspection seems to indicate an implementation that is consistent with the description at `Wolfram MathWorld <http://mathworld.wolfram.com/Scale-FreeNetwork.html>`_ .. function:: filter_stack(graph, head, filters) Perform a depth-first oder walk of the graph starting at *head* and apply all filter functions in *filters* on the node data of the nodes found. Returns (*visited*, *removes*, *orphans*), where * *visited*: the set of visited nodes * *removes*: the list of nodes where the node data doesn't match all *filters*. * *orphans*: list of tuples (*last_good*, *node*), where node is not in *removes* and one of the nodes that is connected by an incoming edge is in *removes*. *Last_good* is the closest upstream node that is not in *removes*.