在有向圖中檢測循環 Python

Question

我正在嘗試從看起來像這樣的文本文件中提取有向圖（1：是節點，第二個數字是鄰居，然后是權重、鄰居、權重等：

1: 2 3 4 5 6 2
2: 3 -4
3: 8 4
4: 5 6
5: 4 -3 8 8
6: 7 3
7: 6 -6 8 7
8:

下面是我的代碼：

fileName = ("graphin_Fig1.txt")
dictionary = {}     # allocate dictionary space
with open(fileName,'r') as file:    # open file
    for line in file:   # read each line of the file
        tokens = line.strip().split(' ')    # separate each number, remove white space
        node = int (tokens[0].split(':')[0])    # remove :, separate node from neighbors and weights
        pos = 1 # initialize counter        
        listtups = []   # allocate array to hold neghbors and weights
        while pos < len(tokens):  # while end of line has not been reached              
            listtups.append((int(tokens[pos]), int (tokens[pos++1])))   # add ints to array
            pos += 2    # counter
        if len(listtups) > 0:   # if neigbors and edges are detected
            dictionary[node] = listtups    # add to nodes
print (dictionary)
  

這是 output：

 `{1: [(2, 3), (4, 5), (6, 2)], 2: [(3, -4)], 3: [(8, 4)], 4: [(5, 6)], 5: [(4, -3), (8, 8)], 6: [(7, 3)], 7: [(6, -6), (8, 7)]}`

我正在嘗試將我的字典用於其他算法，但只有當字典看起來像下面的示例時它們才會起作用：

dictionary = {
    1: {2: 3, 4: 5, 6: 2},
    2: {3: -4},
    3: {8: 4},
    4: {5: 6},
    5: {4: -3, 8: 8},
    6: {7: 3},
    7: {6: -6, 8: 7},
    8: {}
}

我是 python 的新手，真的很掙扎。 如何更改我的代碼以使我提取的字典看起來像上面的示例？

Answer 1

你很親密。 剩下的唯一事情就是將您的元組列表轉換為字典，而不是：

dictionary[node] = listtups    # add to nodes

嘗試

dictionary[node] = dict(listtups)

並刪除檢查鄰居長度的if語句，因為您的示例顯示即使沒有相鄰節點，您也希望添加節點。

Answer 2

好吧，您根本沒有相同的數據結構。 你想要的是一個包含字典的字典。 例如：

outer_d = {"inner_d":{...}, ...}

你正在做的是一個字典，每個鍵的值不是字典，而是一個列表（元組），例如：

outer_d = {"key":[...], ... }

你明白其中的區別嗎？

fileName = ("graphin_Fig1.txt")
dictionary = {}     
with open(fileName,'r') as file:    
    for line in file:  
        tokens = line.strip().split(' ')
        node = int (tokens[0].split(':')[0]) 
        pos = 1 # initialize counter        
        listtups = {}   # another dictionnary, not a list!
        while pos < len(tokens): 
            listtups[int(tokens[pos])] =  int(tokens[pos++1]) 
            pos += 2    # counter
        if len(listtups) > 0:
            dictionary[node] = listtups 
print (dictionary)

產生：

{1: {2: 3, 4: 5, 6: 2}, 2: {3: -4}, 3: {8: 4}, 4: {5: 6}, 5: {4: -3, 8: 8}, 6: {7: 3}, 7: {6: -6, 8: 7}}