How do I generate an adjacency matrix of a graph from a dictionary in python?

问题

I have the following dictionary:

g = {
'A': ['A', 'B', 'C'], 
'B': ['A', 'C', 'E'], 
'C': ['A', 'B', 'D'],
'D': ['C','E'],
'E': ['B','D']
}

It implements a graph, each list contains the neighbors of the graph vertices (dictionary keys are the vertices itself). I'm in trouble, I can not think of a way to get a graph adjacency matrix from their lists of neighbors, might be easy but I am new to python, I hope someone can help me! I am using Python 3.5

I need to generate the following matrix:

回答1:

without pandas

keys=sorted(g.keys())
size=len(keys)

M = [ [0]*size for i in range(size) ]

for a,b in [(keys.index(a), keys.index(b)) for a, row in g.items() for b in row]:
     M[a][b] = 2 if (a==b) else 1

M

[2, 1, 1, 0, 0],
[1, 0, 1, 0, 1],
[1, 1, 0, 1, 0],
[0, 0, 1, 0, 1],
[0, 1, 0, 1, 0]]

Explanation

for a, row in g.items() iterates over the key:value entries in dictionary, and for b in row iterates over the values. If we used (a,b), this would have given us all the pairs.

(keys.index(a), keys.index(b)) But we need the index to assign to the corresponding matrix entry,

keys=sorted(g.keys()) that's why we extracted and sorted the keys.

for a,b in... getting the index entries and assigning value 1 or 2 based on diagonal element or not.

M = [ [0]*size for ... matrix cannot be used before initialization.

回答2:

Here is a solution using pandas.

import pandas as pd

g = {
'A': [ 'A', 'B', 'C'], 
'B': [ 'A', 'C', 'E'], 
'C': [ 'A', 'B ',' D '], # I added a comma here
'D': [' C ',' E '],
'E': [' B ',' D ']
}

# clean up the example
g = {k: [v.strip() for v in vs] for k, vs in g.items()}

edges = [(a, b) for a, bs in g.items() for b in bs]

df = pd.DataFrame(edges)

adj_matrix = pd.crosstab(df[0], df[1])

# 1  A  B  C  D  E
# 0               
# A  1  1  1  0  0
# B  1  0  1  0  1
# C  1  1  0  1  0
# D  0  0  1  0  1
# E  0  1  0  1  0

I am not sure why you have 2 in your example matrix in (A, A) position.

回答3:

import numpy as np
mat = np.zeros(shape = (len(g), len(g)))
for k, vs in g.items():
    for v in vs:
        if v in g[k]:
            mat[k][v] = 1

来源：https://stackoverflow.com/questions/37353759/how-do-i-generate-an-adjacency-matrix-of-a-graph-from-a-dictionary-in-python

标签

python

python-3.x

dictionary

matrix

adjacency-matrix