CODEWITHSUNDEEP
pythonlistdictionarymatrix
Sook Yee Lim
Sook Yee Lim

Reputation: 101

How to read adjacency matrix into a a dict?

I have this file that has this adjacency matrix:

a:g:w:Q:front:Z 
0 2 0 9 12 0 
2 0 15 2 0 0 
0 15 0 7 2 0
9 2 7 0 3 5 
12 0 2 3 0 2
0 0 0 5 2 0

From the matrix,we can see that a is not connected to a but is connected to g,Q,front In python I read the file and put the alphabets into a separate list and the numbers into a list of list.

verticeName=['a','g','w','Q', 'front','z']
adjacency_list=[[0 2 0 9 12 0],[ 2 0 15 2 0 0 ],[0 15 0 7 2 0],[9 2 7 0 3  5 ],[12 0 2 3 0 2],[0 0 0 5 2 0]]

But I want to read this into a dict format so that I can easily modify it later.How do change it to this:

graph = { "a" : ["g","Q","front"],
          "g" : ["a", "W","Q"],
          "w" : ["g", "Q", "front", ],
          "Q" : ["a","g","w","front,"z"],
          "front" : ["a", "w","Q","z"],
          "z"     :["Q"]

          }

Basically the left side is the vertice and the right side is the vertices it connects to.

Upvotes: 0

Views: 651

Answers (2)

tkhurana96
tkhurana96

Reputation: 939

This may help:

vertices_names = []

from collections import defaultdict
graph = defaultdict(list)

with open('your_file_name') as f:
    for line_num, line in enumerate(f):
        line = line.strip()
        if line_num == 0:
            # set cols names
            vertices_names = line.split(':')
        else:
            for idx, each_number in enumerate(line.split(' ')):
                if int(each_number) > 0:
                    append_to = vertices_names[line_num-1]
                    append_what = vertices_names[idx]
                    graph[append_to].append(append_what)

print("graph is:")
for key, value in graph.items():
    print(key, ":", value)

For your given input, the output of the above code is:

graph is:
w : ['g', 'Q', 'front']
Q : ['a', 'g', 'w', 'front', 'Z']
Z : ['Q', 'front']
front : ['a', 'w', 'Q', 'Z']
g : ['a', 'w', 'Q']
a : ['g', 'Q', 'front']

As you asked in comments about the weight of every edge also being stored, so here it is:

vertices_names = []

from collections import defaultdict
graph = defaultdict(list)

with open('data') as f:
    for line_num, line in enumerate(f):
        line = line.strip()
        if line_num == 0:
            # set cols names
            vertices_names = line.split(':')
        else:
            for idx, each_number in enumerate(line.split(' ')):
                if int(each_number) > 0:
                    append_to = vertices_names[line_num-1]
                    append_what = (vertices_names[idx], int(each_number))
                    graph[append_to].append(append_what)

print("graph is:")
for key, value in graph.items():
    print(key, ":", value)

Output of this updated code on your given input is:

graph is:
front : [('a', 12), ('w', 2), ('Q', 3), ('Z', 2)]
w : [('g', 15), ('Q', 7), ('front', 2)]
Q : [('a', 9), ('g', 2), ('w', 7), ('front', 3), ('Z', 5)]
a : [('g', 2), ('Q', 9), ('front', 12)]
Z : [('Q', 5), ('front', 2)]
g : [('a', 2), ('w', 15), ('Q', 2)]

Upvotes: 1

ijkl26
ijkl26

Reputation: 83

You can read names as you do now:

names = ['a', 'g', 'w', 'Q', 'front', 'z']

And then create dictionary of empty lists like this:

graph = {}
for name in names:
    graph[name] = []

Then just read the file and add vertices to proper list in dictionary if there exists an edge:

for source in names:
line = read_line_from_file()  # Not a real function
costs = [int(x) for x in line.split()]
for i in range(6):
    if costs[i]:
        graph[source].append(names[i])

I hope I got your question right.

Upvotes: 0

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