relabel_nodes

relabel_nodes(G, mapping, copy=True)

Relabel the nodes of the graph G according to a given mapping.

The original node ordering may not be preserved if copy is False and the mapping includes overlap between old and new labels.

Parameters:

Ggraph

A NetworkX graph

mappingdictionary

A dictionary with the old labels as keys and new labels as values. A partial mapping is allowed. Mapping 2 nodes to a single node is allowed. Any non-node keys in the mapping are ignored.

copybool (optional, default=True)

If True return a copy, or if False relabel the nodes in place.

See also

convert_node_labels_to_integers

Notes

Only the nodes specified in the mapping will be relabeled. Any non-node keys in the mapping are ignored.

The keyword setting copy=False modifies the graph in place. Relabel_nodes avoids naming collisions by building a directed graph from mapping which specifies the order of relabelings. Naming collisions, such as a->b, b->c, are ordered such that “b” gets renamed to “c” before “a” gets renamed “b”. In cases of circular mappings (e.g. a->b, b->a), modifying the graph is not possible in-place and an exception is raised. In that case, use copy=True.

If a relabel operation on a multigraph would cause two or more edges to have the same source, target and key, the second edge must be assigned a new key to retain all edges. The new key is set to the lowest non-negative integer not already used as a key for edges between these two nodes. Note that this means non-numeric keys may be replaced by numeric keys.

Examples

To create a new graph with nodes relabeled according to a given dictionary:

>>> G = nx.path_graph(3)
>>> sorted(G)
[0, 1, 2]
>>> mapping = {0: "a", 1: "b", 2: "c"}
>>> H = nx.relabel_nodes(G, mapping)
>>> sorted(H)
['a', 'b', 'c']

Nodes can be relabeled with any hashable object, including numbers and strings:

>>> import string
>>> G = nx.path_graph(26)  # nodes are integers 0 through 25
>>> sorted(G)[:3]
[0, 1, 2]
>>> mapping = dict(zip(G, string.ascii_lowercase))
>>> G = nx.relabel_nodes(G, mapping)  # nodes are characters a through z
>>> sorted(G)[:3]
['a', 'b', 'c']
>>> mapping = dict(zip(G, range(1, 27)))
>>> G = nx.relabel_nodes(G, mapping)  # nodes are integers 1 through 26
>>> sorted(G)[:3]
[1, 2, 3]

To perform a partial in-place relabeling, provide a dictionary mapping only a subset of the nodes, and set the copy keyword argument to False:

>>> G = nx.path_graph(3)  # nodes 0-1-2
>>> mapping = {0: "a", 1: "b"}  # 0->'a' and 1->'b'
>>> G = nx.relabel_nodes(G, mapping, copy=False)
>>> sorted(G, key=str)
[2, 'a', 'b']

A mapping can also be given as a function:

>>> G = nx.path_graph(3)
>>> H = nx.relabel_nodes(G, lambda x: x ** 2)
>>> list(H)
[0, 1, 4]

In a multigraph, relabeling two or more nodes to the same new node will retain all edges, but may change the edge keys in the process:

>>> G = nx.MultiGraph()
>>> G.add_edge(0, 1, value="a")  # returns the key for this edge
0
>>> G.add_edge(0, 2, value="b")
0
>>> G.add_edge(0, 3, value="c")
0
>>> mapping = {1: 4, 2: 4, 3: 4}
>>> H = nx.relabel_nodes(G, mapping, copy=True)
>>> print(H[0])
{4: {0: {'value': 'a'}, 1: {'value': 'b'}, 2: {'value': 'c'}}}

This works for in-place relabeling too:

>>> G = nx.relabel_nodes(G, mapping, copy=False)
>>> print(G[0])
{4: {0: {'value': 'a'}, 1: {'value': 'b'}, 2: {'value': 'c'}}}