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Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/classes/function.py')
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diff --git a/.venv/lib/python3.12/site-packages/networkx/classes/function.py b/.venv/lib/python3.12/site-packages/networkx/classes/function.py new file mode 100644 index 00000000..7f42f93e --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/classes/function.py @@ -0,0 +1,1407 @@ +"""Functional interface to graph methods and assorted utilities.""" + +from collections import Counter +from itertools import chain + +import networkx as nx +from networkx.utils import not_implemented_for, pairwise + +__all__ = [ + "nodes", + "edges", + "degree", + "degree_histogram", + "neighbors", + "number_of_nodes", + "number_of_edges", + "density", + "is_directed", + "freeze", + "is_frozen", + "subgraph", + "induced_subgraph", + "edge_subgraph", + "restricted_view", + "to_directed", + "to_undirected", + "add_star", + "add_path", + "add_cycle", + "create_empty_copy", + "set_node_attributes", + "get_node_attributes", + "remove_node_attributes", + "set_edge_attributes", + "get_edge_attributes", + "remove_edge_attributes", + "all_neighbors", + "non_neighbors", + "non_edges", + "common_neighbors", + "is_weighted", + "is_negatively_weighted", + "is_empty", + "selfloop_edges", + "nodes_with_selfloops", + "number_of_selfloops", + "path_weight", + "is_path", +] + + +def nodes(G): + """Returns a NodeView over the graph nodes. + + This function wraps the :func:`G.nodes <networkx.Graph.nodes>` property. + """ + return G.nodes() + + +def edges(G, nbunch=None): + """Returns an edge view of edges incident to nodes in nbunch. + + Return all edges if nbunch is unspecified or nbunch=None. + + For digraphs, edges=out_edges + + This function wraps the :func:`G.edges <networkx.Graph.edges>` property. + """ + return G.edges(nbunch) + + +def degree(G, nbunch=None, weight=None): + """Returns a degree view of single node or of nbunch of nodes. + If nbunch is omitted, then return degrees of *all* nodes. + + This function wraps the :func:`G.degree <networkx.Graph.degree>` property. + """ + return G.degree(nbunch, weight) + + +def neighbors(G, n): + """Returns an iterator over all neighbors of node n. + + This function wraps the :func:`G.neighbors <networkx.Graph.neighbors>` function. + """ + return G.neighbors(n) + + +def number_of_nodes(G): + """Returns the number of nodes in the graph. + + This function wraps the :func:`G.number_of_nodes <networkx.Graph.number_of_nodes>` function. + """ + return G.number_of_nodes() + + +def number_of_edges(G): + """Returns the number of edges in the graph. + + This function wraps the :func:`G.number_of_edges <networkx.Graph.number_of_edges>` function. + """ + return G.number_of_edges() + + +def density(G): + r"""Returns the density of a graph. + + The density for undirected graphs is + + .. math:: + + d = \frac{2m}{n(n-1)}, + + and for directed graphs is + + .. math:: + + d = \frac{m}{n(n-1)}, + + where `n` is the number of nodes and `m` is the number of edges in `G`. + + Notes + ----- + The density is 0 for a graph without edges and 1 for a complete graph. + The density of multigraphs can be higher than 1. + + Self loops are counted in the total number of edges so graphs with self + loops can have density higher than 1. + """ + n = number_of_nodes(G) + m = number_of_edges(G) + if m == 0 or n <= 1: + return 0 + d = m / (n * (n - 1)) + if not G.is_directed(): + d *= 2 + return d + + +def degree_histogram(G): + """Returns a list of the frequency of each degree value. + + Parameters + ---------- + G : Networkx graph + A graph + + Returns + ------- + hist : list + A list of frequencies of degrees. + The degree values are the index in the list. + + Notes + ----- + Note: the bins are width one, hence len(list) can be large + (Order(number_of_edges)) + """ + counts = Counter(d for n, d in G.degree()) + return [counts.get(i, 0) for i in range(max(counts) + 1 if counts else 0)] + + +def is_directed(G): + """Return True if graph is directed.""" + return G.is_directed() + + +def frozen(*args, **kwargs): + """Dummy method for raising errors when trying to modify frozen graphs""" + raise nx.NetworkXError("Frozen graph can't be modified") + + +def freeze(G): + """Modify graph to prevent further change by adding or removing + nodes or edges. + + Node and edge data can still be modified. + + Parameters + ---------- + G : graph + A NetworkX graph + + Examples + -------- + >>> G = nx.path_graph(4) + >>> G = nx.freeze(G) + >>> try: + ... G.add_edge(4, 5) + ... except nx.NetworkXError as err: + ... print(str(err)) + Frozen graph can't be modified + + Notes + ----- + To "unfreeze" a graph you must make a copy by creating a new graph object: + + >>> graph = nx.path_graph(4) + >>> frozen_graph = nx.freeze(graph) + >>> unfrozen_graph = nx.Graph(frozen_graph) + >>> nx.is_frozen(unfrozen_graph) + False + + See Also + -------- + is_frozen + """ + G.add_node = frozen + G.add_nodes_from = frozen + G.remove_node = frozen + G.remove_nodes_from = frozen + G.add_edge = frozen + G.add_edges_from = frozen + G.add_weighted_edges_from = frozen + G.remove_edge = frozen + G.remove_edges_from = frozen + G.clear = frozen + G.clear_edges = frozen + G.frozen = True + return G + + +def is_frozen(G): + """Returns True if graph is frozen. + + Parameters + ---------- + G : graph + A NetworkX graph + + See Also + -------- + freeze + """ + try: + return G.frozen + except AttributeError: + return False + + +def add_star(G_to_add_to, nodes_for_star, **attr): + """Add a star to Graph G_to_add_to. + + The first node in `nodes_for_star` is the middle of the star. + It is connected to all other nodes. + + Parameters + ---------- + G_to_add_to : graph + A NetworkX graph + nodes_for_star : iterable container + A container of nodes. + attr : keyword arguments, optional (default= no attributes) + Attributes to add to every edge in star. + + See Also + -------- + add_path, add_cycle + + Examples + -------- + >>> G = nx.Graph() + >>> nx.add_star(G, [0, 1, 2, 3]) + >>> nx.add_star(G, [10, 11, 12], weight=2) + """ + nlist = iter(nodes_for_star) + try: + v = next(nlist) + except StopIteration: + return + G_to_add_to.add_node(v) + edges = ((v, n) for n in nlist) + G_to_add_to.add_edges_from(edges, **attr) + + +def add_path(G_to_add_to, nodes_for_path, **attr): + """Add a path to the Graph G_to_add_to. + + Parameters + ---------- + G_to_add_to : graph + A NetworkX graph + nodes_for_path : iterable container + A container of nodes. A path will be constructed from + the nodes (in order) and added to the graph. + attr : keyword arguments, optional (default= no attributes) + Attributes to add to every edge in path. + + See Also + -------- + add_star, add_cycle + + Examples + -------- + >>> G = nx.Graph() + >>> nx.add_path(G, [0, 1, 2, 3]) + >>> nx.add_path(G, [10, 11, 12], weight=7) + """ + nlist = iter(nodes_for_path) + try: + first_node = next(nlist) + except StopIteration: + return + G_to_add_to.add_node(first_node) + G_to_add_to.add_edges_from(pairwise(chain((first_node,), nlist)), **attr) + + +def add_cycle(G_to_add_to, nodes_for_cycle, **attr): + """Add a cycle to the Graph G_to_add_to. + + Parameters + ---------- + G_to_add_to : graph + A NetworkX graph + nodes_for_cycle: iterable container + A container of nodes. A cycle will be constructed from + the nodes (in order) and added to the graph. + attr : keyword arguments, optional (default= no attributes) + Attributes to add to every edge in cycle. + + See Also + -------- + add_path, add_star + + Examples + -------- + >>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc + >>> nx.add_cycle(G, [0, 1, 2, 3]) + >>> nx.add_cycle(G, [10, 11, 12], weight=7) + """ + nlist = iter(nodes_for_cycle) + try: + first_node = next(nlist) + except StopIteration: + return + G_to_add_to.add_node(first_node) + G_to_add_to.add_edges_from( + pairwise(chain((first_node,), nlist), cyclic=True), **attr + ) + + +def subgraph(G, nbunch): + """Returns the subgraph induced on nodes in nbunch. + + Parameters + ---------- + G : graph + A NetworkX graph + + nbunch : list, iterable + A container of nodes that will be iterated through once (thus + it should be an iterator or be iterable). Each element of the + container should be a valid node type: any hashable type except + None. If nbunch is None, return all edges data in the graph. + Nodes in nbunch that are not in the graph will be (quietly) + ignored. + + Notes + ----- + subgraph(G) calls G.subgraph() + """ + return G.subgraph(nbunch) + + +def induced_subgraph(G, nbunch): + """Returns a SubGraph view of `G` showing only nodes in nbunch. + + The induced subgraph of a graph on a set of nodes N is the + graph with nodes N and edges from G which have both ends in N. + + Parameters + ---------- + G : NetworkX Graph + nbunch : node, container of nodes or None (for all nodes) + + Returns + ------- + subgraph : SubGraph View + A read-only view of the subgraph in `G` induced by the nodes. + Changes to the graph `G` will be reflected in the view. + + Notes + ----- + To create a mutable subgraph with its own copies of nodes + edges and attributes use `subgraph.copy()` or `Graph(subgraph)` + + For an inplace reduction of a graph to a subgraph you can remove nodes: + `G.remove_nodes_from(n in G if n not in set(nbunch))` + + If you are going to compute subgraphs of your subgraphs you could + end up with a chain of views that can be very slow once the chain + has about 15 views in it. If they are all induced subgraphs, you + can short-cut the chain by making them all subgraphs of the original + graph. The graph class method `G.subgraph` does this when `G` is + a subgraph. In contrast, this function allows you to choose to build + chains or not, as you wish. The returned subgraph is a view on `G`. + + Examples + -------- + >>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc + >>> H = nx.induced_subgraph(G, [0, 1, 3]) + >>> list(H.edges) + [(0, 1)] + >>> list(H.nodes) + [0, 1, 3] + """ + induced_nodes = nx.filters.show_nodes(G.nbunch_iter(nbunch)) + return nx.subgraph_view(G, filter_node=induced_nodes) + + +def edge_subgraph(G, edges): + """Returns a view of the subgraph induced by the specified edges. + + The induced subgraph contains each edge in `edges` and each + node incident to any of those edges. + + Parameters + ---------- + G : NetworkX Graph + edges : iterable + An iterable of edges. Edges not present in `G` are ignored. + + Returns + ------- + subgraph : SubGraph View + A read-only edge-induced subgraph of `G`. + Changes to `G` are reflected in the view. + + Notes + ----- + To create a mutable subgraph with its own copies of nodes + edges and attributes use `subgraph.copy()` or `Graph(subgraph)` + + If you create a subgraph of a subgraph recursively you can end up + with a chain of subgraphs that becomes very slow with about 15 + nested subgraph views. Luckily the edge_subgraph filter nests + nicely so you can use the original graph as G in this function + to avoid chains. We do not rule out chains programmatically so + that odd cases like an `edge_subgraph` of a `restricted_view` + can be created. + + Examples + -------- + >>> G = nx.path_graph(5) + >>> H = G.edge_subgraph([(0, 1), (3, 4)]) + >>> list(H.nodes) + [0, 1, 3, 4] + >>> list(H.edges) + [(0, 1), (3, 4)] + """ + nxf = nx.filters + edges = set(edges) + nodes = set() + for e in edges: + nodes.update(e[:2]) + induced_nodes = nxf.show_nodes(nodes) + if G.is_multigraph(): + if G.is_directed(): + induced_edges = nxf.show_multidiedges(edges) + else: + induced_edges = nxf.show_multiedges(edges) + else: + if G.is_directed(): + induced_edges = nxf.show_diedges(edges) + else: + induced_edges = nxf.show_edges(edges) + return nx.subgraph_view(G, filter_node=induced_nodes, filter_edge=induced_edges) + + +def restricted_view(G, nodes, edges): + """Returns a view of `G` with hidden nodes and edges. + + The resulting subgraph filters out node `nodes` and edges `edges`. + Filtered out nodes also filter out any of their edges. + + Parameters + ---------- + G : NetworkX Graph + nodes : iterable + An iterable of nodes. Nodes not present in `G` are ignored. + edges : iterable + An iterable of edges. Edges not present in `G` are ignored. + + Returns + ------- + subgraph : SubGraph View + A read-only restricted view of `G` filtering out nodes and edges. + Changes to `G` are reflected in the view. + + Notes + ----- + To create a mutable subgraph with its own copies of nodes + edges and attributes use `subgraph.copy()` or `Graph(subgraph)` + + If you create a subgraph of a subgraph recursively you may end up + with a chain of subgraph views. Such chains can get quite slow + for lengths near 15. To avoid long chains, try to make your subgraph + based on the original graph. We do not rule out chains programmatically + so that odd cases like an `edge_subgraph` of a `restricted_view` + can be created. + + Examples + -------- + >>> G = nx.path_graph(5) + >>> H = nx.restricted_view(G, [0], [(1, 2), (3, 4)]) + >>> list(H.nodes) + [1, 2, 3, 4] + >>> list(H.edges) + [(2, 3)] + """ + nxf = nx.filters + hide_nodes = nxf.hide_nodes(nodes) + if G.is_multigraph(): + if G.is_directed(): + hide_edges = nxf.hide_multidiedges(edges) + else: + hide_edges = nxf.hide_multiedges(edges) + else: + if G.is_directed(): + hide_edges = nxf.hide_diedges(edges) + else: + hide_edges = nxf.hide_edges(edges) + return nx.subgraph_view(G, filter_node=hide_nodes, filter_edge=hide_edges) + + +def to_directed(graph): + """Returns a directed view of the graph `graph`. + + Identical to graph.to_directed(as_view=True) + Note that graph.to_directed defaults to `as_view=False` + while this function always provides a view. + """ + return graph.to_directed(as_view=True) + + +def to_undirected(graph): + """Returns an undirected view of the graph `graph`. + + Identical to graph.to_undirected(as_view=True) + Note that graph.to_undirected defaults to `as_view=False` + while this function always provides a view. + """ + return graph.to_undirected(as_view=True) + + +def create_empty_copy(G, with_data=True): + """Returns a copy of the graph G with all of the edges removed. + + Parameters + ---------- + G : graph + A NetworkX graph + + with_data : bool (default=True) + Propagate Graph and Nodes data to the new graph. + + See Also + -------- + empty_graph + + """ + H = G.__class__() + H.add_nodes_from(G.nodes(data=with_data)) + if with_data: + H.graph.update(G.graph) + return H + + +def set_node_attributes(G, values, name=None): + """Sets node attributes from a given value or dictionary of values. + + .. Warning:: The call order of arguments `values` and `name` + switched between v1.x & v2.x. + + Parameters + ---------- + G : NetworkX Graph + + values : scalar value, dict-like + What the node attribute should be set to. If `values` is + not a dictionary, then it is treated as a single attribute value + that is then applied to every node in `G`. This means that if + you provide a mutable object, like a list, updates to that object + will be reflected in the node attribute for every node. + The attribute name will be `name`. + + If `values` is a dict or a dict of dict, it should be keyed + by node to either an attribute value or a dict of attribute key/value + pairs used to update the node's attributes. + + name : string (optional, default=None) + Name of the node attribute to set if values is a scalar. + + Examples + -------- + After computing some property of the nodes of a graph, you may want + to assign a node attribute to store the value of that property for + each node:: + + >>> G = nx.path_graph(3) + >>> bb = nx.betweenness_centrality(G) + >>> isinstance(bb, dict) + True + >>> nx.set_node_attributes(G, bb, "betweenness") + >>> G.nodes[1]["betweenness"] + 1.0 + + If you provide a list as the second argument, updates to the list + will be reflected in the node attribute for each node:: + + >>> G = nx.path_graph(3) + >>> labels = [] + >>> nx.set_node_attributes(G, labels, "labels") + >>> labels.append("foo") + >>> G.nodes[0]["labels"] + ['foo'] + >>> G.nodes[1]["labels"] + ['foo'] + >>> G.nodes[2]["labels"] + ['foo'] + + If you provide a dictionary of dictionaries as the second argument, + the outer dictionary is assumed to be keyed by node to an inner + dictionary of node attributes for that node:: + + >>> G = nx.path_graph(3) + >>> attrs = {0: {"attr1": 20, "attr2": "nothing"}, 1: {"attr2": 3}} + >>> nx.set_node_attributes(G, attrs) + >>> G.nodes[0]["attr1"] + 20 + >>> G.nodes[0]["attr2"] + 'nothing' + >>> G.nodes[1]["attr2"] + 3 + >>> G.nodes[2] + {} + + Note that if the dictionary contains nodes that are not in `G`, the + values are silently ignored:: + + >>> G = nx.Graph() + >>> G.add_node(0) + >>> nx.set_node_attributes(G, {0: "red", 1: "blue"}, name="color") + >>> G.nodes[0]["color"] + 'red' + >>> 1 in G.nodes + False + + """ + # Set node attributes based on type of `values` + if name is not None: # `values` must not be a dict of dict + try: # `values` is a dict + for n, v in values.items(): + try: + G.nodes[n][name] = values[n] + except KeyError: + pass + except AttributeError: # `values` is a constant + for n in G: + G.nodes[n][name] = values + else: # `values` must be dict of dict + for n, d in values.items(): + try: + G.nodes[n].update(d) + except KeyError: + pass + nx._clear_cache(G) + + +def get_node_attributes(G, name, default=None): + """Get node attributes from graph + + Parameters + ---------- + G : NetworkX Graph + + name : string + Attribute name + + default: object (default=None) + Default value of the node attribute if there is no value set for that + node in graph. If `None` then nodes without this attribute are not + included in the returned dict. + + Returns + ------- + Dictionary of attributes keyed by node. + + Examples + -------- + >>> G = nx.Graph() + >>> G.add_nodes_from([1, 2, 3], color="red") + >>> color = nx.get_node_attributes(G, "color") + >>> color[1] + 'red' + >>> G.add_node(4) + >>> color = nx.get_node_attributes(G, "color", default="yellow") + >>> color[4] + 'yellow' + """ + if default is not None: + return {n: d.get(name, default) for n, d in G.nodes.items()} + return {n: d[name] for n, d in G.nodes.items() if name in d} + + +def remove_node_attributes(G, *attr_names, nbunch=None): + """Remove node attributes from all nodes in the graph. + + Parameters + ---------- + G : NetworkX Graph + + *attr_names : List of Strings + The attribute names to remove from the graph. + + nbunch : List of Nodes + Remove the node attributes only from the nodes in this list. + + Examples + -------- + >>> G = nx.Graph() + >>> G.add_nodes_from([1, 2, 3], color="blue") + >>> nx.get_node_attributes(G, "color") + {1: 'blue', 2: 'blue', 3: 'blue'} + >>> nx.remove_node_attributes(G, "color") + >>> nx.get_node_attributes(G, "color") + {} + """ + + if nbunch is None: + nbunch = G.nodes() + + for attr in attr_names: + for n, d in G.nodes(data=True): + if n in nbunch: + try: + del d[attr] + except KeyError: + pass + + +def set_edge_attributes(G, values, name=None): + """Sets edge attributes from a given value or dictionary of values. + + .. Warning:: The call order of arguments `values` and `name` + switched between v1.x & v2.x. + + Parameters + ---------- + G : NetworkX Graph + + values : scalar value, dict-like + What the edge attribute should be set to. If `values` is + not a dictionary, then it is treated as a single attribute value + that is then applied to every edge in `G`. This means that if + you provide a mutable object, like a list, updates to that object + will be reflected in the edge attribute for each edge. The attribute + name will be `name`. + + If `values` is a dict or a dict of dict, it should be keyed + by edge tuple to either an attribute value or a dict of attribute + key/value pairs used to update the edge's attributes. + For multigraphs, the edge tuples must be of the form ``(u, v, key)``, + where `u` and `v` are nodes and `key` is the edge key. + For non-multigraphs, the keys must be tuples of the form ``(u, v)``. + + name : string (optional, default=None) + Name of the edge attribute to set if values is a scalar. + + Examples + -------- + After computing some property of the edges of a graph, you may want + to assign a edge attribute to store the value of that property for + each edge:: + + >>> G = nx.path_graph(3) + >>> bb = nx.edge_betweenness_centrality(G, normalized=False) + >>> nx.set_edge_attributes(G, bb, "betweenness") + >>> G.edges[1, 2]["betweenness"] + 2.0 + + If you provide a list as the second argument, updates to the list + will be reflected in the edge attribute for each edge:: + + >>> labels = [] + >>> nx.set_edge_attributes(G, labels, "labels") + >>> labels.append("foo") + >>> G.edges[0, 1]["labels"] + ['foo'] + >>> G.edges[1, 2]["labels"] + ['foo'] + + If you provide a dictionary of dictionaries as the second argument, + the entire dictionary will be used to update edge attributes:: + + >>> G = nx.path_graph(3) + >>> attrs = {(0, 1): {"attr1": 20, "attr2": "nothing"}, (1, 2): {"attr2": 3}} + >>> nx.set_edge_attributes(G, attrs) + >>> G[0][1]["attr1"] + 20 + >>> G[0][1]["attr2"] + 'nothing' + >>> G[1][2]["attr2"] + 3 + + The attributes of one Graph can be used to set those of another. + + >>> H = nx.path_graph(3) + >>> nx.set_edge_attributes(H, G.edges) + + Note that if the dict contains edges that are not in `G`, they are + silently ignored:: + + >>> G = nx.Graph([(0, 1)]) + >>> nx.set_edge_attributes(G, {(1, 2): {"weight": 2.0}}) + >>> (1, 2) in G.edges() + False + + For multigraphs, the `values` dict is expected to be keyed by 3-tuples + including the edge key:: + + >>> MG = nx.MultiGraph() + >>> edges = [(0, 1), (0, 1)] + >>> MG.add_edges_from(edges) # Returns list of edge keys + [0, 1] + >>> attributes = {(0, 1, 0): {"cost": 21}, (0, 1, 1): {"cost": 7}} + >>> nx.set_edge_attributes(MG, attributes) + >>> MG[0][1][0]["cost"] + 21 + >>> MG[0][1][1]["cost"] + 7 + + If MultiGraph attributes are desired for a Graph, you must convert the 3-tuple + multiedge to a 2-tuple edge and the last multiedge's attribute value will + overwrite the previous values. Continuing from the previous case we get:: + + >>> H = nx.path_graph([0, 1, 2]) + >>> nx.set_edge_attributes(H, {(u, v): ed for u, v, ed in MG.edges.data()}) + >>> nx.get_edge_attributes(H, "cost") + {(0, 1): 7} + + """ + if name is not None: + # `values` does not contain attribute names + try: + # if `values` is a dict using `.items()` => {edge: value} + if G.is_multigraph(): + for (u, v, key), value in values.items(): + try: + G._adj[u][v][key][name] = value + except KeyError: + pass + else: + for (u, v), value in values.items(): + try: + G._adj[u][v][name] = value + except KeyError: + pass + except AttributeError: + # treat `values` as a constant + for u, v, data in G.edges(data=True): + data[name] = values + else: + # `values` consists of doct-of-dict {edge: {attr: value}} shape + if G.is_multigraph(): + for (u, v, key), d in values.items(): + try: + G._adj[u][v][key].update(d) + except KeyError: + pass + else: + for (u, v), d in values.items(): + try: + G._adj[u][v].update(d) + except KeyError: + pass + nx._clear_cache(G) + + +def get_edge_attributes(G, name, default=None): + """Get edge attributes from graph + + Parameters + ---------- + G : NetworkX Graph + + name : string + Attribute name + + default: object (default=None) + Default value of the edge attribute if there is no value set for that + edge in graph. If `None` then edges without this attribute are not + included in the returned dict. + + Returns + ------- + Dictionary of attributes keyed by edge. For (di)graphs, the keys are + 2-tuples of the form: (u, v). For multi(di)graphs, the keys are 3-tuples of + the form: (u, v, key). + + Examples + -------- + >>> G = nx.Graph() + >>> nx.add_path(G, [1, 2, 3], color="red") + >>> color = nx.get_edge_attributes(G, "color") + >>> color[(1, 2)] + 'red' + >>> G.add_edge(3, 4) + >>> color = nx.get_edge_attributes(G, "color", default="yellow") + >>> color[(3, 4)] + 'yellow' + """ + if G.is_multigraph(): + edges = G.edges(keys=True, data=True) + else: + edges = G.edges(data=True) + if default is not None: + return {x[:-1]: x[-1].get(name, default) for x in edges} + return {x[:-1]: x[-1][name] for x in edges if name in x[-1]} + + +def remove_edge_attributes(G, *attr_names, ebunch=None): + """Remove edge attributes from all edges in the graph. + + Parameters + ---------- + G : NetworkX Graph + + *attr_names : List of Strings + The attribute names to remove from the graph. + + Examples + -------- + >>> G = nx.path_graph(3) + >>> nx.set_edge_attributes(G, {(u, v): u + v for u, v in G.edges()}, name="weight") + >>> nx.get_edge_attributes(G, "weight") + {(0, 1): 1, (1, 2): 3} + >>> remove_edge_attributes(G, "weight") + >>> nx.get_edge_attributes(G, "weight") + {} + """ + if ebunch is None: + ebunch = G.edges(keys=True) if G.is_multigraph() else G.edges() + + for attr in attr_names: + edges = ( + G.edges(keys=True, data=True) if G.is_multigraph() else G.edges(data=True) + ) + for *e, d in edges: + if tuple(e) in ebunch: + try: + del d[attr] + except KeyError: + pass + + +def all_neighbors(graph, node): + """Returns all of the neighbors of a node in the graph. + + If the graph is directed returns predecessors as well as successors. + + Parameters + ---------- + graph : NetworkX graph + Graph to find neighbors. + + node : node + The node whose neighbors will be returned. + + Returns + ------- + neighbors : iterator + Iterator of neighbors + """ + if graph.is_directed(): + values = chain(graph.predecessors(node), graph.successors(node)) + else: + values = graph.neighbors(node) + return values + + +def non_neighbors(graph, node): + """Returns the non-neighbors of the node in the graph. + + Parameters + ---------- + graph : NetworkX graph + Graph to find neighbors. + + node : node + The node whose neighbors will be returned. + + Returns + ------- + non_neighbors : set + Set of nodes in the graph that are not neighbors of the node. + """ + return graph._adj.keys() - graph._adj[node].keys() - {node} + + +def non_edges(graph): + """Returns the nonexistent edges in the graph. + + Parameters + ---------- + graph : NetworkX graph. + Graph to find nonexistent edges. + + Returns + ------- + non_edges : iterator + Iterator of edges that are not in the graph. + """ + if graph.is_directed(): + for u in graph: + for v in non_neighbors(graph, u): + yield (u, v) + else: + nodes = set(graph) + while nodes: + u = nodes.pop() + for v in nodes - set(graph[u]): + yield (u, v) + + +@not_implemented_for("directed") +def common_neighbors(G, u, v): + """Returns the common neighbors of two nodes in a graph. + + Parameters + ---------- + G : graph + A NetworkX undirected graph. + + u, v : nodes + Nodes in the graph. + + Returns + ------- + cnbors : set + Set of common neighbors of u and v in the graph. + + Raises + ------ + NetworkXError + If u or v is not a node in the graph. + + Examples + -------- + >>> G = nx.complete_graph(5) + >>> sorted(nx.common_neighbors(G, 0, 1)) + [2, 3, 4] + """ + if u not in G: + raise nx.NetworkXError("u is not in the graph.") + if v not in G: + raise nx.NetworkXError("v is not in the graph.") + + return G._adj[u].keys() & G._adj[v].keys() - {u, v} + + +def is_weighted(G, edge=None, weight="weight"): + """Returns True if `G` has weighted edges. + + Parameters + ---------- + G : graph + A NetworkX graph. + + edge : tuple, optional + A 2-tuple specifying the only edge in `G` that will be tested. If + None, then every edge in `G` is tested. + + weight: string, optional + The attribute name used to query for edge weights. + + Returns + ------- + bool + A boolean signifying if `G`, or the specified edge, is weighted. + + Raises + ------ + NetworkXError + If the specified edge does not exist. + + Examples + -------- + >>> G = nx.path_graph(4) + >>> nx.is_weighted(G) + False + >>> nx.is_weighted(G, (2, 3)) + False + + >>> G = nx.DiGraph() + >>> G.add_edge(1, 2, weight=1) + >>> nx.is_weighted(G) + True + + """ + if edge is not None: + data = G.get_edge_data(*edge) + if data is None: + msg = f"Edge {edge!r} does not exist." + raise nx.NetworkXError(msg) + return weight in data + + if is_empty(G): + # Special handling required since: all([]) == True + return False + + return all(weight in data for u, v, data in G.edges(data=True)) + + +@nx._dispatchable(edge_attrs="weight") +def is_negatively_weighted(G, edge=None, weight="weight"): + """Returns True if `G` has negatively weighted edges. + + Parameters + ---------- + G : graph + A NetworkX graph. + + edge : tuple, optional + A 2-tuple specifying the only edge in `G` that will be tested. If + None, then every edge in `G` is tested. + + weight: string, optional + The attribute name used to query for edge weights. + + Returns + ------- + bool + A boolean signifying if `G`, or the specified edge, is negatively + weighted. + + Raises + ------ + NetworkXError + If the specified edge does not exist. + + Examples + -------- + >>> G = nx.Graph() + >>> G.add_edges_from([(1, 3), (2, 4), (2, 6)]) + >>> G.add_edge(1, 2, weight=4) + >>> nx.is_negatively_weighted(G, (1, 2)) + False + >>> G[2][4]["weight"] = -2 + >>> nx.is_negatively_weighted(G) + True + >>> G = nx.DiGraph() + >>> edges = [("0", "3", 3), ("0", "1", -5), ("1", "0", -2)] + >>> G.add_weighted_edges_from(edges) + >>> nx.is_negatively_weighted(G) + True + + """ + if edge is not None: + data = G.get_edge_data(*edge) + if data is None: + msg = f"Edge {edge!r} does not exist." + raise nx.NetworkXError(msg) + return weight in data and data[weight] < 0 + + return any(weight in data and data[weight] < 0 for u, v, data in G.edges(data=True)) + + +def is_empty(G): + """Returns True if `G` has no edges. + + Parameters + ---------- + G : graph + A NetworkX graph. + + Returns + ------- + bool + True if `G` has no edges, and False otherwise. + + Notes + ----- + An empty graph can have nodes but not edges. The empty graph with zero + nodes is known as the null graph. This is an $O(n)$ operation where n + is the number of nodes in the graph. + + """ + return not any(G._adj.values()) + + +def nodes_with_selfloops(G): + """Returns an iterator over nodes with self loops. + + A node with a self loop has an edge with both ends adjacent + to that node. + + Returns + ------- + nodelist : iterator + A iterator over nodes with self loops. + + See Also + -------- + selfloop_edges, number_of_selfloops + + Examples + -------- + >>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc + >>> G.add_edge(1, 1) + >>> G.add_edge(1, 2) + >>> list(nx.nodes_with_selfloops(G)) + [1] + + """ + return (n for n, nbrs in G._adj.items() if n in nbrs) + + +def selfloop_edges(G, data=False, keys=False, default=None): + """Returns an iterator over selfloop edges. + + A selfloop edge has the same node at both ends. + + Parameters + ---------- + G : graph + A NetworkX graph. + data : string or bool, optional (default=False) + Return selfloop edges as two tuples (u, v) (data=False) + or three-tuples (u, v, datadict) (data=True) + or three-tuples (u, v, datavalue) (data='attrname') + keys : bool, optional (default=False) + If True, return edge keys with each edge. + default : value, optional (default=None) + Value used for edges that don't have the requested attribute. + Only relevant if data is not True or False. + + Returns + ------- + edgeiter : iterator over edge tuples + An iterator over all selfloop edges. + + See Also + -------- + nodes_with_selfloops, number_of_selfloops + + Examples + -------- + >>> G = nx.MultiGraph() # or Graph, DiGraph, MultiDiGraph, etc + >>> ekey = G.add_edge(1, 1) + >>> ekey = G.add_edge(1, 2) + >>> list(nx.selfloop_edges(G)) + [(1, 1)] + >>> list(nx.selfloop_edges(G, data=True)) + [(1, 1, {})] + >>> list(nx.selfloop_edges(G, keys=True)) + [(1, 1, 0)] + >>> list(nx.selfloop_edges(G, keys=True, data=True)) + [(1, 1, 0, {})] + """ + if data is True: + if G.is_multigraph(): + if keys is True: + return ( + (n, n, k, d) + for n, nbrs in G._adj.items() + if n in nbrs + for k, d in nbrs[n].items() + ) + else: + return ( + (n, n, d) + for n, nbrs in G._adj.items() + if n in nbrs + for d in nbrs[n].values() + ) + else: + return ((n, n, nbrs[n]) for n, nbrs in G._adj.items() if n in nbrs) + elif data is not False: + if G.is_multigraph(): + if keys is True: + return ( + (n, n, k, d.get(data, default)) + for n, nbrs in G._adj.items() + if n in nbrs + for k, d in nbrs[n].items() + ) + else: + return ( + (n, n, d.get(data, default)) + for n, nbrs in G._adj.items() + if n in nbrs + for d in nbrs[n].values() + ) + else: + return ( + (n, n, nbrs[n].get(data, default)) + for n, nbrs in G._adj.items() + if n in nbrs + ) + else: + if G.is_multigraph(): + if keys is True: + return ( + (n, n, k) + for n, nbrs in G._adj.items() + if n in nbrs + for k in nbrs[n] + ) + else: + return ( + (n, n) + for n, nbrs in G._adj.items() + if n in nbrs + for i in range(len(nbrs[n])) # for easy edge removal (#4068) + ) + else: + return ((n, n) for n, nbrs in G._adj.items() if n in nbrs) + + +def number_of_selfloops(G): + """Returns the number of selfloop edges. + + A selfloop edge has the same node at both ends. + + Returns + ------- + nloops : int + The number of selfloops. + + See Also + -------- + nodes_with_selfloops, selfloop_edges + + Examples + -------- + >>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc + >>> G.add_edge(1, 1) + >>> G.add_edge(1, 2) + >>> nx.number_of_selfloops(G) + 1 + """ + return sum(1 for _ in nx.selfloop_edges(G)) + + +def is_path(G, path): + """Returns whether or not the specified path exists. + + For it to return True, every node on the path must exist and + each consecutive pair must be connected via one or more edges. + + Parameters + ---------- + G : graph + A NetworkX graph. + + path : list + A list of nodes which defines the path to traverse + + Returns + ------- + bool + True if `path` is a valid path in `G` + + """ + try: + return all(nbr in G._adj[node] for node, nbr in nx.utils.pairwise(path)) + except (KeyError, TypeError): + return False + + +def path_weight(G, path, weight): + """Returns total cost associated with specified path and weight + + Parameters + ---------- + G : graph + A NetworkX graph. + + path: list + A list of node labels which defines the path to traverse + + weight: string + A string indicating which edge attribute to use for path cost + + Returns + ------- + cost: int or float + An integer or a float representing the total cost with respect to the + specified weight of the specified path + + Raises + ------ + NetworkXNoPath + If the specified edge does not exist. + """ + multigraph = G.is_multigraph() + cost = 0 + + if not nx.is_path(G, path): + raise nx.NetworkXNoPath("path does not exist") + for node, nbr in nx.utils.pairwise(path): + if multigraph: + cost += min(v[weight] for v in G._adj[node][nbr].values()) + else: + cost += G._adj[node][nbr][weight] + return cost |