407 lines
13 KiB
Python
407 lines
13 KiB
Python
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"""Functions to convert NetworkX graphs to and from other formats.
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The preferred way of converting data to a NetworkX graph is through the
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graph constructor. The constructor calls the to_networkx_graph() function
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which attempts to guess the input type and convert it automatically.
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Examples
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--------
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Create a graph with a single edge from a dictionary of dictionaries
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>>> d = {0: {1: 1}} # dict-of-dicts single edge (0,1)
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>>> G = nx.Graph(d)
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See Also
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--------
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nx_agraph, nx_pydot
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"""
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import warnings
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import networkx as nx
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from collections.abc import Collection, Generator, Iterator
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__all__ = [
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"to_networkx_graph",
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"from_dict_of_dicts",
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"to_dict_of_dicts",
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"from_dict_of_lists",
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"to_dict_of_lists",
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"from_edgelist",
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"to_edgelist",
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]
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def to_networkx_graph(data, create_using=None, multigraph_input=False):
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"""Make a NetworkX graph from a known data structure.
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The preferred way to call this is automatically
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from the class constructor
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>>> d = {0: {1: {"weight": 1}}} # dict-of-dicts single edge (0,1)
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>>> G = nx.Graph(d)
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instead of the equivalent
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>>> G = nx.from_dict_of_dicts(d)
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Parameters
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----------
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data : object to be converted
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Current known types are:
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any NetworkX graph
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dict-of-dicts
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dict-of-lists
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container (e.g. set, list, tuple) of edges
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iterator (e.g. itertools.chain) that produces edges
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generator of edges
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Pandas DataFrame (row per edge)
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numpy matrix
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numpy ndarray
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scipy sparse matrix
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pygraphviz agraph
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create_using : NetworkX graph constructor, optional (default=nx.Graph)
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Graph type to create. If graph instance, then cleared before populated.
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multigraph_input : bool (default False)
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If True and data is a dict_of_dicts,
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try to create a multigraph assuming dict_of_dict_of_lists.
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If data and create_using are both multigraphs then create
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a multigraph from a multigraph.
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"""
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# NX graph
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if hasattr(data, "adj"):
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try:
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result = from_dict_of_dicts(
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data.adj,
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create_using=create_using,
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multigraph_input=data.is_multigraph(),
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)
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if hasattr(data, "graph"): # data.graph should be dict-like
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result.graph.update(data.graph)
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if hasattr(data, "nodes"): # data.nodes should be dict-like
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# result.add_node_from(data.nodes.items()) possible but
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# for custom node_attr_dict_factory which may be hashable
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# will be unexpected behavior
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for n, dd in data.nodes.items():
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result._node[n].update(dd)
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return result
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except Exception as e:
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raise nx.NetworkXError("Input is not a correct NetworkX graph.") from e
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# pygraphviz agraph
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if hasattr(data, "is_strict"):
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try:
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return nx.nx_agraph.from_agraph(data, create_using=create_using)
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except Exception as e:
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raise nx.NetworkXError("Input is not a correct pygraphviz graph.") from e
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# dict of dicts/lists
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if isinstance(data, dict):
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try:
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return from_dict_of_dicts(
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data, create_using=create_using, multigraph_input=multigraph_input
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)
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except:
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try:
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return from_dict_of_lists(data, create_using=create_using)
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except Exception as e:
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raise TypeError("Input is not known type.") from e
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# Pandas DataFrame
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try:
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import pandas as pd
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if isinstance(data, pd.DataFrame):
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if data.shape[0] == data.shape[1]:
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try:
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return nx.from_pandas_adjacency(data, create_using=create_using)
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except Exception as e:
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msg = "Input is not a correct Pandas DataFrame adjacency matrix."
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raise nx.NetworkXError(msg) from e
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else:
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try:
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return nx.from_pandas_edgelist(
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data, edge_attr=True, create_using=create_using
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)
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except Exception as e:
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msg = "Input is not a correct Pandas DataFrame edge-list."
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raise nx.NetworkXError(msg) from e
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except ImportError:
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msg = "pandas not found, skipping conversion test."
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warnings.warn(msg, ImportWarning)
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# numpy matrix or ndarray
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try:
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import numpy
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if isinstance(data, (numpy.matrix, numpy.ndarray)):
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try:
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return nx.from_numpy_matrix(data, create_using=create_using)
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except Exception as e:
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raise nx.NetworkXError(
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"Input is not a correct numpy matrix or array."
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) from e
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except ImportError:
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warnings.warn("numpy not found, skipping conversion test.", ImportWarning)
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# scipy sparse matrix - any format
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try:
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import scipy
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if hasattr(data, "format"):
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try:
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return nx.from_scipy_sparse_matrix(data, create_using=create_using)
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except Exception as e:
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raise nx.NetworkXError(
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"Input is not a correct scipy sparse matrix type."
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) from e
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except ImportError:
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warnings.warn("scipy not found, skipping conversion test.", ImportWarning)
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# Note: most general check - should remain last in order of execution
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# Includes containers (e.g. list, set, dict, etc.), generators, and
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# iterators (e.g. itertools.chain) of edges
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if isinstance(data, (Collection, Generator, Iterator)):
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try:
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return from_edgelist(data, create_using=create_using)
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except Exception as e:
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raise nx.NetworkXError("Input is not a valid edge list") from e
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raise nx.NetworkXError("Input is not a known data type for conversion.")
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def to_dict_of_lists(G, nodelist=None):
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"""Returns adjacency representation of graph as a dictionary of lists.
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Parameters
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----------
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G : graph
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A NetworkX graph
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nodelist : list
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Use only nodes specified in nodelist
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Notes
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-----
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Completely ignores edge data for MultiGraph and MultiDiGraph.
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"""
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if nodelist is None:
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nodelist = G
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d = {}
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for n in nodelist:
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d[n] = [nbr for nbr in G.neighbors(n) if nbr in nodelist]
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return d
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def from_dict_of_lists(d, create_using=None):
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"""Returns a graph from a dictionary of lists.
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Parameters
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----------
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d : dictionary of lists
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A dictionary of lists adjacency representation.
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create_using : NetworkX graph constructor, optional (default=nx.Graph)
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Graph type to create. If graph instance, then cleared before populated.
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Examples
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--------
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>>> dol = {0: [1]} # single edge (0,1)
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>>> G = nx.from_dict_of_lists(dol)
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or
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>>> G = nx.Graph(dol) # use Graph constructor
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"""
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G = nx.empty_graph(0, create_using)
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G.add_nodes_from(d)
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if G.is_multigraph() and not G.is_directed():
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# a dict_of_lists can't show multiedges. BUT for undirected graphs,
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# each edge shows up twice in the dict_of_lists.
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# So we need to treat this case separately.
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seen = {}
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for node, nbrlist in d.items():
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for nbr in nbrlist:
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if nbr not in seen:
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G.add_edge(node, nbr)
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seen[node] = 1 # don't allow reverse edge to show up
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else:
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G.add_edges_from(
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((node, nbr) for node, nbrlist in d.items() for nbr in nbrlist)
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)
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return G
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def to_dict_of_dicts(G, nodelist=None, edge_data=None):
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"""Returns adjacency representation of graph as a dictionary of dictionaries.
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Parameters
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----------
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G : graph
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A NetworkX graph
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nodelist : list
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Use only nodes specified in nodelist
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edge_data : list, optional
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If provided, the value of the dictionary will be
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set to edge_data for all edges. This is useful to make
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an adjacency matrix type representation with 1 as the edge data.
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If edgedata is None, the edgedata in G is used to fill the values.
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If G is a multigraph, the edgedata is a dict for each pair (u,v).
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"""
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dod = {}
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if nodelist is None:
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if edge_data is None:
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for u, nbrdict in G.adjacency():
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dod[u] = nbrdict.copy()
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else: # edge_data is not None
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for u, nbrdict in G.adjacency():
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dod[u] = dod.fromkeys(nbrdict, edge_data)
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else: # nodelist is not None
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if edge_data is None:
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for u in nodelist:
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dod[u] = {}
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for v, data in ((v, data) for v, data in G[u].items() if v in nodelist):
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dod[u][v] = data
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else: # nodelist and edge_data are not None
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for u in nodelist:
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dod[u] = {}
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for v in (v for v in G[u] if v in nodelist):
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dod[u][v] = edge_data
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return dod
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def from_dict_of_dicts(d, create_using=None, multigraph_input=False):
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"""Returns a graph from a dictionary of dictionaries.
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Parameters
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----------
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d : dictionary of dictionaries
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A dictionary of dictionaries adjacency representation.
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create_using : NetworkX graph constructor, optional (default=nx.Graph)
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Graph type to create. If graph instance, then cleared before populated.
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multigraph_input : bool (default False)
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When True, the values of the inner dict are assumed
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to be containers of edge data for multiple edges.
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Otherwise this routine assumes the edge data are singletons.
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Examples
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--------
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>>> dod = {0: {1: {"weight": 1}}} # single edge (0,1)
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>>> G = nx.from_dict_of_dicts(dod)
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or
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>>> G = nx.Graph(dod) # use Graph constructor
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"""
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G = nx.empty_graph(0, create_using)
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G.add_nodes_from(d)
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# is dict a MultiGraph or MultiDiGraph?
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if multigraph_input:
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# make a copy of the list of edge data (but not the edge data)
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if G.is_directed():
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if G.is_multigraph():
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G.add_edges_from(
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(u, v, key, data)
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for u, nbrs in d.items()
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for v, datadict in nbrs.items()
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for key, data in datadict.items()
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)
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else:
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G.add_edges_from(
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(u, v, data)
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for u, nbrs in d.items()
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for v, datadict in nbrs.items()
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for key, data in datadict.items()
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)
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else: # Undirected
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if G.is_multigraph():
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seen = set() # don't add both directions of undirected graph
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for u, nbrs in d.items():
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for v, datadict in nbrs.items():
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if (u, v) not in seen:
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G.add_edges_from(
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(u, v, key, data) for key, data in datadict.items()
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)
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seen.add((v, u))
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else:
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seen = set() # don't add both directions of undirected graph
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for u, nbrs in d.items():
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for v, datadict in nbrs.items():
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if (u, v) not in seen:
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G.add_edges_from(
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(u, v, data) for key, data in datadict.items()
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)
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seen.add((v, u))
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else: # not a multigraph to multigraph transfer
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if G.is_multigraph() and not G.is_directed():
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# d can have both representations u-v, v-u in dict. Only add one.
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# We don't need this check for digraphs since we add both directions,
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# or for Graph() since it is done implicitly (parallel edges not allowed)
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seen = set()
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for u, nbrs in d.items():
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for v, data in nbrs.items():
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if (u, v) not in seen:
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G.add_edge(u, v, key=0)
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G[u][v][0].update(data)
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seen.add((v, u))
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else:
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G.add_edges_from(
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((u, v, data) for u, nbrs in d.items() for v, data in nbrs.items())
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)
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return G
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def to_edgelist(G, nodelist=None):
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"""Returns a list of edges in the graph.
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Parameters
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----------
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G : graph
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A NetworkX graph
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nodelist : list
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Use only nodes specified in nodelist
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"""
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if nodelist is None:
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return G.edges(data=True)
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return G.edges(nodelist, data=True)
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def from_edgelist(edgelist, create_using=None):
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"""Returns a graph from a list of edges.
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Parameters
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----------
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edgelist : list or iterator
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Edge tuples
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create_using : NetworkX graph constructor, optional (default=nx.Graph)
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Graph type to create. If graph instance, then cleared before populated.
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Examples
|
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|
|
--------
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>>> edgelist = [(0, 1)] # single edge (0,1)
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>>> G = nx.from_edgelist(edgelist)
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|
or
|
||
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|
||
|
|
>>> G = nx.Graph(edgelist) # use Graph constructor
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||
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|
||
|
|
"""
|
||
|
|
G = nx.empty_graph(0, create_using)
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||
|
|
G.add_edges_from(edgelist)
|
||
|
|
return G
|