Representing a network in Python
I have a vertices such as dic = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, 'f': 5, 'n':6, 'm':7, 'g':8}
and i have two columns as follows represent the relationship between the vertices :
a a
b d
e f
c f
n f
m g
I want to associate each vertex in the first column with the corresponding vertex in the second column by an edge. So a
with a
is represent a l开发者_开发知识库oop. b
with d
is fine. e
,c
and n
they are sharing the same vertex f
. Instead to say e
with f
, c
with f
and n
with f
we can say e
, c
and n
with f
.
See: https://www.python.org/doc/essays/graphs/
graph = {
'a' : [ 'a' ],
'b' : [ 'd' ],
'c' : [ 'f' ],
'd' : [],
'e' : [ 'f' ],
'f' : [],
'g' : [],
'm' : [ 'g' ],
'n' : [ 'f' ]
}
print [ vertex for vertex, edges in graph.items() if 'f' in edges ]
EDIT:
Ok, it sounds like you just want a function to build the graph from your given inputs?
Something like this:
def build_graph( vertices, edges ):
graph = dict( (v, list()) for v in vertices.keys() )
for a, b in edges:
graph[ a ].append( b )
return graph
If you need help parsing your columnar data into a list of two-tuples then that's a different question entirely
The general alternative to @kurosch's answer (adjacency list) is called an adjacency matrix. It's simply a matrix representing every possible edge where 1 indicates presence of an edge, 0 not.
adj = [[0 for x in range(len(dic)] for x in range(len(dic))]
adj[dic['a'][dic['b']] = 1
etc..
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