Note

This is the documentation for the current state of the development branch of rustworkx. The documentation or APIs here can change prior to being released.

PyDAG#

class PyDAG(check_cycle=False, multigraph=True, attrs=None, *, node_count_hint=None, edge_count_hint=None)[source]#

Bases: PyDiGraph

A class for creating direct acyclic graphs.

PyDAG is just an alias of the PyDiGraph class and behaves identically to the PyDiGraph class and can be used interchangeably with PyDiGraph. It currently exists solely as a backwards compatibility alias for users of rustworkx from prior to the 0.4.0 release when there was no PyDiGraph class.

The PyDAG class is used to create a directed graph. It can be a multigraph (have multiple edges between nodes). Each node and edge (although rarely used for edges) is indexed by an integer id. These ids are stable for the lifetime of the graph object and on node or edge deletions you can have holes in the list of indices for the graph. Node indices will be reused on additions after removal. For example:

import rustworkx as rx

graph = rx.PyDAG()
graph.add_nodes_from(list(range(5)))
graph.add_nodes_from(list(range(2)))
graph.remove_node(2)
print("After deletion:", graph.node_indices())
res_manual = graph.add_parent(6, None, None)
print("After adding a new node:", graph.node_indices())
After deletion: NodeIndices[0, 1, 3, 4, 5, 6]
After adding a new node: NodeIndices[0, 1, 2, 3, 4, 5, 6]

Additionally, each node and edge contains an arbitrary Python object as a weight/data payload.

You can use the index for access to the data payload as in the following example:

import rustworkx as rx

graph = rx.PyDAG()
data_payload = "An arbitrary Python object"
node_index = graph.add_node(data_payload)
print("Node Index: %s" % node_index)
print(graph[node_index])
Node Index: 0
An arbitrary Python object

The PyDAG class implements the Python mapping protocol for nodes so in addition to access you can also update the data payload with:

import rustworkx as rx

graph = rx.PyDAG()
data_payload = "An arbitrary Python object"
node_index = graph.add_node(data_payload)
graph[node_index] = "New Payload"
print("Node Index: %s" % node_index)
print(graph[node_index])
Node Index: 0
New Payload

The PyDAG class has an option for real time cycle checking which can be used to ensure any edges added to the graph does not introduce a cycle. By default the real time cycle checking feature is disabled for performance, however you can enable it by setting the check_cycle attribute to True. For example:

import rustworkx as rx
dag = rx.PyDAG()
dag.check_cycle = True

or at object creation:

import rustworkx as rx
dag = rx.PyDAG(check_cycle=True)

With check_cycle set to true any calls to PyDAG.add_edge() will ensure that no cycles are added, ensuring that the PyDAG class truly represents a directed acyclic graph. Do note that this cycle checking on add_edge(), add_edges_from(), add_edges_from_no_data(), extend_from_edge_list(), and extend_from_weighted_edge_list() comes with a performance penalty that grows as the graph does. If you’re adding a node and edge at the same time, leveraging PyDAG.add_child() or PyDAG.add_parent() will avoid this overhead.

By default a PyDAG is a multigraph (meaning there can be parallel edges between nodes) however this can be disabled by setting the multigraph kwarg to False when calling the PyDAG constructor. For example:

import rustworkx as rx
dag = rx.PyDAG(multigraph=False)

This can only be set at PyDiGraph initialization and not adjusted after creation. When multigraph is set to False if a method call is made that would add a parallel edge it will instead update the existing edge’s weight/data payload.

The maximum number of nodes and edges allowed on a PyGraph object is \(2^{32} - 1\) (4,294,967,294) each. Attempting to add more nodes or edges than this will result in an exception being raised.

Parameters:
  • check_cycle (bool) – When this is set to True the created PyDAG has runtime cycle detection enabled.

  • multgraph (bool) – When this is set to False the created PyDAG object will not be a multigraph. When False if a method call is made that would add parallel edges the the weight/weight from that method call will be used to update the existing edge in place.

Methods

add_child

Add a new child node to the graph.

add_edge

Add an edge between 2 nodes.

add_edges_from

Add new edges to the dag.

add_edges_from_no_data

Add new edges to the dag without python data.

add_node

Add a new node to the graph.

add_nodes_from

Add new nodes to the graph.

add_parent

Add a new parent node to the dag.

adj

Get the index and data for the neighbors of a node.

adj_direction

Get the index and data for either the parent or children of a node.

clear

Clear all nodes and edges

clear_edges

Clears all edges, leaves nodes intact

compose

Add another PyDiGraph object into this PyDiGraph

contract_nodes

Substitute a set of nodes with a single new node.

copy

Return a shallow copy of the graph

edge_index_map

Get an edge index map

edge_indices

Return a list of all edge indices.

edge_indices_from_endpoints

Return a list of indices of all directed edges between specified nodes

edge_list

Get edge list

edge_subgraph

Return a new PyDiGraph object for an edge induced subgraph of this graph

edges

Return a list of all edge data.

extend_from_edge_list

Extend graph from an edge list

extend_from_weighted_edge_list

Extend graph from a weighted edge list

filter_edges

Filters a graph's edges by some criteria conditioned on a edge's data payload and returns those edges' indices.

filter_nodes

Filters a graph's nodes by some criteria conditioned on a node's data payload and returns those nodes' indices.

find_adjacent_node_by_edge

Find a target node with a specific edge

find_node_by_weight

Find node within this graph given a specific weight

find_predecessor_node_by_edge

Find a source node with a specific edge

find_predecessors_by_edge

Return a filtered list of predecessor data such that each node has at least one edge data which matches the filter.

find_successors_by_edge

Return a filtered list of successors data such that each node has at least one edge data which matches the filter.

from_adjacency_matrix

Create a new PyDiGraph object from an adjacency matrix with matrix elements of type float

from_complex_adjacency_matrix

Create a new PyDiGraph object from an adjacency matrix with matrix elements of type complex

get_all_edge_data

Return the edge data for all the edges between 2 nodes.

get_edge_data

Return the edge data for an edge between 2 nodes.

get_edge_data_by_index

Return the edge data for the edge by its given index

get_edge_endpoints_by_index

Return the edge endpoints for the edge by its given index

get_node_data

Return the node data for a given node index

has_edge

Return True if there is an edge from node_a to node_b.

has_node

Return True if there is a node in the graph.

has_parallel_edges

Detect if the graph has parallel edges or not

in_degree

Get the degree of a node for inbound edges.

in_edges

Get the index and edge data for all parents of a node.

incident_edge_index_map

Return the index map of edges incident to a provided node

incident_edges

Return the list of edge indices incident to a provided node

insert_node_on_in_edges

Insert a node between a reference node and all its predecessor nodes

insert_node_on_in_edges_multiple

Insert a node between a list of reference nodes and all their predecessors

insert_node_on_out_edges

Insert a node between a reference node and all its successor nodes

insert_node_on_out_edges_multiple

Insert a node between a list of reference nodes and all their successors

is_symmetric

Check if the graph is symmetric

make_symmetric

Make edges in graph symmetric

merge_nodes

Merge two nodes in the graph.

neighbors

Get the neighbors (i.e.

neighbors_undirected

Get the direction-agnostic neighbors (i.e.

node_indexes

Return a list of all node indices.

node_indices

Return a list of all node indices.

nodes

Return a list of all node data.

num_edges

Return the number of edges in the graph

num_nodes

Return the number of nodes in the graph

out_degree

Get the degree of a node for outbound edges.

out_edges

Get the index and edge data for all children of a node.

predecessor_indices

Get the predecessor indices of a node.

predecessors

Return a list of all the node predecessor data.

read_edge_list

Read an edge list file and create a new PyDiGraph object from the contents

remove_edge

Remove an edge between 2 nodes.

remove_edge_from_index

Remove an edge identified by the provided index

remove_edges_from

Remove edges from the graph.

remove_node

Remove a node from the graph.

remove_node_retain_edges

Remove a node from the graph and add edges from all predecessors to all successors

remove_node_retain_edges_by_id

Remove a node from the graph and add edges from predecessors to successors in cases where an incoming and outgoing edge have the same weight by Python object identity.

remove_node_retain_edges_by_key

Remove a node from the graph and add edges from predecessors to successors in cases where an incoming and outgoing edge have the same weight by Python object equality.

remove_nodes_from

Remove nodes from the graph.

reverse

Reverse the direction of all edges in the graph, in place.

subgraph

Return a new PyDiGraph object for a subgraph of this graph

substitute_node_with_subgraph

Substitute a node with a PyDigraph object

successor_indices

Get the successor indices of a node.

successors

Return a list of all the node successor data.

to_dot

Generate a dot file from the graph

to_undirected

Generate a new PyGraph object from this graph

update_edge

Update an edge's weight/payload inplace

update_edge_by_index

Update an edge's weight/payload by the edge index

weighted_edge_list

Get edge list with weights

write_edge_list

Write an edge list file from the PyDiGraph object

Attributes

attrs#
check_cycle#

Whether cycle checking is enabled for the DiGraph/DAG.

If set to True adding new edges that would introduce a cycle will raise a DAGWouldCycle exception.

multigraph#

Whether the graph is a multigraph (allows multiple edges between nodes) or not

If set to False multiple edges between nodes are not allowed and calls that would add a parallel edge will instead update the existing edge