pygraph-tool

pygraph-tool is a module to create and manipulate graphs. Nodes can be all objects who you want and edges are oriented and valued at 1 by default. If you wish one graph not oriented, edges must be declared in one direction and then in the other.

Getting started

Import modules

Graph module:

from pygraph_tool import Graph

Exceptions module:

from pygraph_tool import (
    NodeException,
    EdgeException,
    GraphException
)

Others modules (optional):

from pygraph_tool import Node, Edge

Create new graph

The new graph is empty (No node and no edge).

graph: Graph = Graph()

Create new nodes in graph

Create new nodes n1, n2 and n3, three nodes of graph.

graph.add_node("I'm n1", "n1")
graph.add_node("I'm n2", "n2")
graph.add_node("I'm n3", "n3")

If node already exists(same id), the GraphException is raise.

try:
    graph.add_node("I'm n1 again", "n1")
except GraphException as error:
    pass  # or do something...

If an argument is None, the NodeException is raise.

Create new unidirectional edge in graph

Create new edges e1 such as n1->n2 with weight = 1.5, e2 such as n3->n2 with weight by default = 1 and e3 such as n1->n3 with weight by default = 1

graph.add_unidirectional_edge("n1", "n2", "e1", 1.5)
graph.add_unidirectional_edge("n3", "n2", "e2")
graph.add_unidirectional_edge("n1", "n3", "e3")

If edge already exists (same id), the GraphException is raise.

try:
    graph.add_unidirectional_edge("n2", "n3", "e1")
except GraphException as error:
    pass  # or do something...

If an argument (except weight argument) is None, the EdgeException is raise.

Create new bidirectional edge in graph

coming soon...

Remove node

If node doesn't exist in graph, GraphException is raise.

try:
    graph.remove_node("n2")
except GraphException as error:
    pass  # or do something...

Remove edge

If edge doesn't exist in graph, GraphException is raise.

try:
    graph.remove_edge("e3")
except GraphException as error:
    pass  # or do something...

Visualize the graph (very simple representation)

Create function for display graph

def displayGraph(graph: Graph) -> None:
    # display the graph's nodes
    for node in graph.nodes:
        print(f"{node.node_id}: {node.node_content}")

    # display the graph's edges
    for edge in graph.edges:
        message: str = (
            f"{edge.node_start.node_id} "
            f"--- {edge.edge_id} = {edge.weight} ---> "
            f"{edge.node_end.node_id}"
        )
        print(message)


# Display graph
displayGraph(graph)

Author

If you have any questions or suggestions, please don't hesitate to contact me : belaich.david@outlook.fr.