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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=[]):

self.start = start

self.end = end

self.path = path

self.path+=[self.start]

if self.start == self.end:

return self.path

if not self.graph.has_key(self.start):

return None

for node in self.graph[self.start]:

if node not in self.path:

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

if newpath:

return newpath

return None

def find_all_path(self, start, end, path=[]):

self.start = start

self.end = end

self.path = path

self.path+=[self.start]

if self.start == self.end:

return [self.path]

if not self.graph.has_key(self.start):

return []

paths=[]

for node in self.graph[self.start]:

if node not in self.path:

newpaths = self.find_all_path(node, self.end, self.path)

for newpath in newpaths:

paths.append(newpath)

return paths

def find_shortest_path(self, start, end, path=[]):

self.start = start

self.end = end

self.path = path

self.path+=[self.start]

if self.start == self.end:

return self.path

if not self.graph.has_key(self.start):

return None

shortest = None

for node in self.graph[self.start]:

if node not in self.path:

newpath = self.find_shortest_path(node, self.end, self.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']

}

#inistialization 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')