def subgraph_view(G, filter_node=no_filter, filter_edge=no_filter):
newG = nx.freeze(G.__class__())
newG._NODE_OK = filter_node
newG._EDGE_OK = filter_edge
# create view by assigning attributes from G
newG._graph = G
newG.graph = G.graph
newG._node = FilterAtlas(G._node, filter_node)
if G.is_multigraph():
Adj = FilterMultiAdjacency
def reverse_edge(u, v, k):
return filter_edge(v, u, k)
else:
Adj = FilterAdjacency
def reverse_edge(u, v):
return filter_edge(v, u)
if G.is_directed():
newG._succ = Adj(G._succ, filter_node, filter_edge)
newG._pred = Adj(G._pred, filter_node, reverse_edge)
newG._adj = newG._succ
else:
newG._adj = Adj(G._adj, filter_node, filter_edge)
return newG
def __init__(self, graph, filter_node=no_filter, filter_edge=no_filter):
self._graph = graph
self._NODE_OK = filter_node
self._EDGE_OK = filter_edge
# Set graph interface
self.graph = graph.graph
self._node = FilterAtlas(graph._node, filter_node)
self._adj = FilterMultiAdjacency(graph._adj, filter_node, filter_edge)
def __init__(self, graph, filter_node=no_filter, filter_edge=no_filter):
self._graph = graph
self._NODE_OK = filter_node
self._EDGE_OK = filter_edge
# Set graph interface
self.graph = graph.graph
self._node = FilterAtlas(graph._node, filter_node)
self._adj = FilterAdjacency(graph._adj, filter_node, filter_edge)
self._pred = FilterAdjacency(graph._pred, filter_node,
lambda u, v: filter_edge(v, u))
self._succ = self._adj
def __init__(self, graph, filter_node=no_filter, filter_edge=no_filter):
self._graph = graph
self.root_graph = graph
while hasattr(self.root_graph, '_graph'):
self.root_graph = self.root_graph._graph
self._NODE_OK = filter_node
self._EDGE_OK = filter_edge
# Set graph interface
self.graph = graph.graph
self._node = FilterAtlas(graph._node, filter_node)
FMA = FilterMultiAdjacency
self._adj = FMA(graph._adj, filter_node, filter_edge)
self._pred = FMA(graph._pred, filter_node,
lambda u, v, k: filter_edge(v, u, k))
self._succ = self._adj
def subgraph_view(G, filter_node=no_filter, filter_edge=no_filter):
"""View of `G` applying a filter on nodes and edges.
`subgraph_view` provides a read-only view of the input graph that excludes
nodes and edges based on the outcome of two filter functions `filter_node`
and `filter_edge`.
The `filter_node` function takes one argument --- the node --- and returns
`True` if the node should be included in the subgraph, and `False` if it
should not be included.
The `filter_edge` function takes two (or three arguments if `G` is a
multi-graph) --- the nodes describing an edge, plus the edge-key if
parallel edges are possible --- and returns `True` if the edge should be
included in the subgraph, and `False` if it should not be included.
Both node and edge filter functions are called on graph elements as they
are queried, meaning there is no up-front cost to creating the view.
Parameters
----------
G : networkx.Graph
A directed/undirected graph/multigraph
filter_node : callable, optional
A function taking a node as input, which returns `True` if the node
should appear in the view.
filter_edge : callable, optional
A function taking as input the two nodes describing an edge (plus the
edge-key if `G` is a multi-graph), which returns `True` if the edge
should appear in the view.
Returns
-------
graph : networkx.Graph
A read-only graph view of the input graph.
Examples
--------
>>> G = nx.path_graph(6)
Filter functions operate on the node, and return `True` if the node should
appear in the view:
>>> def filter_node(n1):
... return n1 != 5
...
>>> view = nx.subgraph_view(G, filter_node=filter_node)
>>> view.nodes()
NodeView((0, 1, 2, 3, 4))
We can use a closure pattern to filter graph elements based on additional
data --- for example, filtering on edge data attached to the graph:
>>> G[3][4]["cross_me"] = False
>>> def filter_edge(n1, n2):
... return G[n1][n2].get("cross_me", True)
...
>>> view = nx.subgraph_view(G, filter_edge=filter_edge)
>>> view.edges()
EdgeView([(0, 1), (1, 2), (2, 3), (4, 5)])
>>> view = nx.subgraph_view(G, filter_node=filter_node, filter_edge=filter_edge,)
>>> view.nodes()
NodeView((0, 1, 2, 3, 4))
>>> view.edges()
EdgeView([(0, 1), (1, 2), (2, 3)])
"""
newG = nx.freeze(G.__class__())
newG._NODE_OK = filter_node
newG._EDGE_OK = filter_edge
# create view by assigning attributes from G
newG._graph = G
newG.graph = G.graph
newG._node = FilterAtlas(G._node, filter_node)
if G.is_multigraph():
Adj = FilterMultiAdjacency
def reverse_edge(u, v, k=None):
return filter_edge(v, u, k)
else:
Adj = FilterAdjacency
def reverse_edge(u, v, k=None):
return filter_edge(v, u)
if G.is_directed():
newG._succ = Adj(G._succ, filter_node, filter_edge)
newG._pred = Adj(G._pred, filter_node, reverse_edge)
newG._adj = newG._succ
else:
newG._adj = Adj(G._adj, filter_node, filter_edge)
return newG
