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#!/usr/bin/env python

# -*- coding: utf-8 -*-

class GraphSearch:

"""Graph search emulation in python, from source

http://www.python.org/doc/essays/graphs/"""

def __init__(self, graph):

self.graph = graph

def find_path(self, start, end, path=None):

path = path or []

path.append(start)

if start == end:

return path

for node in self.graph.get(start, []):

if node not in path:

newpath = self.find_path(node, end, path)

if newpath:

return newpath

def find_all_path(self, start, end, path=None):

path = path or []

path.append(start)

if start == end:

return [path]

paths = []

for node in self.graph.get(start, []):

if node not in path:

newpaths = self.find_all_path(node, end, path[:])

paths.extend(newpaths)

return paths

def find_shortest_path(self, start, end, path=None):

path = path or []

path.append(start)

if start == end:

return path

shortest = None

for node in self.graph.get(start, []):

if node not in path:

newpath = self.find_shortest_path(node, end, path[:])

if newpath:

if not shortest or len(newpath) < len(shortest):

shortest = newpath

return shortest

# example of graph usage

graph = {'A': ['B', 'C'],

'B': ['C', 'D'],

'C': ['D'],

'D': ['C'],

'E': ['F'],

'F': ['C']

}

# initialization of new graph search object

graph1 = GraphSearch(graph)

print(graph1.find_path('A', 'D'))

print(graph1.find_all_path('A', 'D'))

print(graph1.find_shortest_path('A', 'D'))

### OUTPUT ###

# ['A', 'B', 'C', 'D']

# [['A', 'B', 'C', 'D'], ['A', 'B', 'D'], ['A', 'C', 'D']]

# ['A', 'B', 'D']