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: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*.
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