使用字典创建邻接列表

Question

The question asks: A graph can be represented in a file by listing one link per line, with each link represented by a pair of nodes. Write a function that reads such a file and returns an adjacency list (as a dictionary) for the graph. Notice that, for each line AB in the file, your function will need to insert node B into the list of neighbors A and insert node A into the list of neighbors of B . Example of a possible file:

graph.txt
A B
A C
A D
B E
C D
C E 

I expect the final list to look something like this:

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

Answer 1

You can use defaultdict to answer this question. I wrote the code and it is working but you may like to think about it first.

dictAdjacency=defaultdict(list)
with open('C:/graph.txt') as readObj:
    lines=readObj.readlines()
    for line in lines:
        tempList=line.rstrip('\n').split(' ')
        dictAdjacency[tempList[0]].append(tempList[1])
        dictAdjacency[tempList[1]].append(tempList[0])
print(dictAdjacency)

RESULT

defaultdict(<class 'list'>, 
{
  'A': ['B', 'C', 'D'], 
  'B': ['A', 'E'], 
  'C': ['A', 'D', 'E'], 
  'D': ['A', 'C'], 
  'E': ['B', 'C']
})