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digraph.py
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62 lines (54 loc) · 1.89 KB
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from graph import graph
from copy import deepcopy
class digraph(graph):
"""
Directed Graph class - made of nodes and edges
methods: add_edge, add_edges, add_node, add_nodes, has_node,
has_edge, nodes, edges, neighbors, del_node, del_edge, node_order,
set_edge_weight, get_edge_weight,
"""
DEFAULT_WEIGHT = 1
DIRECTED = True
def __init__(self):
self.node_neighbors = {}
def __str__(self):
return "Directed Graph \nNodes: %s \nEdges: %s" % (self.nodes(), self.edges())
def add_edge(self, edge, wt=1, label=""):
"""
Add an edge to the graph connecting two nodes.
An edge, here, is a pair of node like C(m, n) or a tuple
with m as head and n as tail : m -> n
"""
u, v = edge
if (v not in self.node_neighbors[u]):
self.node_neighbors[u][v] = wt
else:
raise Exception("Edge (%s, %s) already added in the graph" % (u, v))
def del_edge(self, edge):
"""
Deletes an edge from a graph. An edge, here, is a pair like
C(m,n) or a tuple
"""
u, v = edge
if not self.has_edge(edge):
raise Exception("Edge (%s, %s) not an existing edge" % (u, v))
del self.node_neighbors[u][v]
def del_node(self, node):
"""
Deletes a node from a graph
"""
for each in list(self.neighbors(node)):
if (each != node):
self.del_edge((node, each))
for n in self.nodes():
if self.has_edge((n, node)):
self.del_edge((n, node))
del(self.node_neighbors[node])
def get_transpose(self):
""" Returns the transpose of the graph
with edges reversed and nodes same """
digr = deepcopy(self)
for (u, v) in self.edges():
digr.del_edge((u, v))
digr.add_edge((v, u))
return digr