graph-theory 2020.1.30.50866

A graph library

graph-theory

A simple graph library...
... A bit like networkx, just without the overhead...
... similar to graph-tool, without the Python 2.7 legacy...
... with code that you can explain to your boss..."

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Install:

pip install graph-theory

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Import:

import Graph
g = Graph()

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Modules:

module	description
from graph import Graph, Graph3D	Elementary methods (see basic methods below) for Graph and Graph3D.
from graph.assignment_problem import ...	solvers for assignment problem, the Weapons-Target Assignment Problem, ...
from graph.flow_problem import ...	maximum flow
from graph.hash import ...	graph hash functions: graph hash, merkle tree, flow graph hash
from graph.random import ...	graph generators for random, 2D and 3D graphs.
from graph.scheduling import sp_solver	Scheduling problem solver.
from graph.search import ...	shortest path, breadth-first, depth-first
from graph.topology import ...	Topological comparisons and operators: make/assert subgraph, detect partitions, path comparisons, cycle detection, path verification, network range
from graph.transform import ...	Isomorphic transformation methods like adjacency matrix, all-pairs-shortest path, etc.

All module functions are available from Graph, Graph2D and Graph3D (where applicable).

methods	description
a in g	assert if g contains node a
g.add_node(n, [obj])	adds a node (with a pointer to object obj if given)
g.node(node1)	returns object attached to node 1.
g.del_node(node1)	deletes node1 and all it's edges.
g.nodes()	returns a list of nodes
len(g.nodes())	returns the number of nodes
g.nodes(from_node=1)	returns nodes with edges from node 1
g.nodes(to_node=2)	returns nodes with edges to node 2
g.nodes(in_degree=2)	returns nodes with 2 incoming edges
g.nodes(out_degree=2)	returns nodes with 2 outgoing edges
g.add_edge(1,2,3)	adds edge to g for vector (1,2) with value 3
g.edge(1,2)	returns value of edge between nodes 1 and 2
g.edge(1,2,default=3)	returns default=3 if edge(1,2) doesn't exist. similar to d.get(key, 3)
g.del_edge(1,2)	removes edge between nodes 1 and 2
g.edges(path=[path])	returns a list of edges (along a path if given).
g.edges(from_node=1)	returns edges outgoing from node 1
g.edges(to_node=2)	returns edges incoming to node 2
len(g.edges())	returns the number of edges
g.from_dict(d)	updates the graph from a dictionary
g.to_dict()	dumps the graph as a dictionary
g.from_list(L)	updates the graph from a list
g.to_list()	dumps the graph as a list of edges
g.shortest_path(start,end)	finds the path with smallest edge sum
g.breadth_first_search(start,end)	finds the with least number of hops
g.depth_first_search(start,end)	finds a path between 2 nodes (start, end) using DFS and backtracking.
g.distance_from_path(path)	finds the distance following a given path.
g.maximum_flow(source,sink)	finds the maximum flow between a source and a sink
g.solve_tsp()	solves the traveling salesman problem for the graph
g.is_subgraph(g2)	determines if graph g2 is a subgraph in g.
g.is_partite(n)	determines if graph is n-partite
g.has_cycles()	determines if there are cycles in the graph
g.same_path(p1,p2)	compares two paths, returns True if they're the same.
g.adjacency_matrix()	returns the adjacency matrix for the graph.
g.all_pairs_shortest_paths()	finds the shortest path between all nodes.
g.shortest_tree_all_pairs()	finds the shortest tree for all pairs.
g.has_path(p)	asserts whether a path p exists in g.
g.all_paths(start,end)	finds all combinations of paths between 2 nodes.

FAQ

want to	doesn't work	do instead	but why?
have multiple edges between two nodes	Graph(from_list=[(1,2,3), (1,2,4)]	Add dummy nodes [(1,a,3), (a,2,0), (1,b,4),(b,2,0)]	Explicit is better than implicit.
multiple values on an edge	g.add_edge(1,2,{'a':3, 'b':4})	Have two graphs g_a.add_edge(1,2,3) g_b.add_edge(1,2,4)	Most graph algorithms don't work with multiple values

Specialised modules:

from graph import Graph
from graph import Graph3D
from graph.hashing import merkle_tree
from graph.assignment_problem import ap_solver
from graph.assignment_problem import wtap_solver
from graph.scheduling_problem import sp_solver

Examples contains a number of tutorial/solutions to common operations research and computer science problems, which are made simple when treated as a graph.

module	function	description
assignment_problem.py	assignment_problem	solves the assignment problem
hashgraph.py	merkle_tree	datablocks
hashgraph.py	graph_hash	computes the sha256 of a graphs nodes and edges
hashgraph.py	flow_graph_hash	computes the sha256 of a graph with multiple sources and sinks
knapsack_problem.py	knapsack problem	solves the knapsack problem
wtap.py	weapons-target assignment problem	solves the WTAP problem.