dgl.DGLGraph.add_nodes

DGLGraph.add_nodes(num, data=None, ntype=None)[source]

Add new nodes of the same node type

Parameters:

num (int) – Number of nodes to add.
data (dict, optional) – Feature data of the added nodes.
ntype (str, optional) – The type of the new nodes. Can be omitted if there is only one node type in the graph.

Notes

Inplace update is applied to the current graph.
If the key of data does not contain some existing feature fields, those features for the new nodes will be created by initializers defined with set_n_initializer() (default initializer fills zeros).
If the key of data contains new feature fields, those features for the old nodes will be created by initializers defined with set_n_initializer() (default initializer fills zeros).
This function discards the batch information. Please use dgl.DGLGraph.set_batch_num_nodes() and dgl.DGLGraph.set_batch_num_edges() on the transformed graph to maintain the information.

Examples

The following example uses PyTorch backend.

>>> import dgl
>>> import torch

Homogeneous Graphs or Heterogeneous Graphs with A Single Node Type

>>> g = dgl.graph((torch.tensor([0, 1]), torch.tensor([1, 2])))
>>> g.num_nodes()
3
>>> g.add_nodes(2)
>>> g.num_nodes()
5

If the graph has some node features and new nodes are added without features, their features will be created by initializers defined with set_n_initializer().

>>> g.ndata['h'] = torch.ones(5, 1)
>>> g.add_nodes(1)
>>> g.ndata['h']
tensor([[1.], [1.], [1.], [1.], [1.], [0.]])

We can also assign features for the new nodes in adding new nodes.

>>> g.add_nodes(1, {'h': torch.ones(1, 1), 'w': torch.ones(1, 1)})
>>> g.ndata['h']
tensor([[1.], [1.], [1.], [1.], [1.], [0.], [1.]])

Since data contains new feature fields, the features for old nodes will be created by initializers defined with set_n_initializer().

>>> g.ndata['w']
tensor([[0.], [0.], [0.], [0.], [0.], [0.], [1.]])

Heterogeneous Graphs with Multiple Node Types

>>> g = dgl.heterograph({
...     ('user', 'plays', 'game'): (torch.tensor([0, 1, 1, 2]),
...                                 torch.tensor([0, 0, 1, 1])),
...     ('developer', 'develops', 'game'): (torch.tensor([0, 1]),
...                                         torch.tensor([0, 1]))
...     })
>>> g.add_nodes(2)
DGLError: Node type name must be specified
if there are more than one node types.
>>> g.num_nodes('user')
3
>>> g.add_nodes(2, ntype='user')
>>> g.num_nodes('user')
5