为节点分配颜色时出现 KeyError

Question

我在尝试创建网络时收到 KeyError。

我的数据集是

Node    Neighbors       Colour  Weight
 Luke   Alte            orange    3
 Luke   John            orange    3
Michael Laura           red       43
Ludo    Stella          orange   21
Alte    Ludo            blue     24
Alte    Luke            blue     24

上面的table按节点显示链接：

节点卢克与阿尔特和约翰有联系。它的边权重为 3，颜色为橙色
节点迈克尔与劳拉有联系。它的重量为 43，颜色为红色
node Ludo 与 Stella 关联。它的权重为 21，颜色为橙色
node Alte 与 Luke 和 Ludo 有联系。它有蓝色和重量 24

做如下：

NROWS = None
def get_graph_from_pandas(df):
    
    G = nx.DiGraph() # assuming the graph is directed since e.g node 1 has 
                     # 3 as neighbour but 3 doesnt have 1 as neighbour
    
    
    for row in df.itertuples(): # row is the row of the dataframe
        n = row.Node
        w = row.Weight
        c = row.Colour
        neighbors = row.Neighbors
        
        G.add_node(n, weight = w, colour = c)
        
        for neigh in neighbors:
            #add edge weights here, attribute of G.add_edge
            G.add_edge(n,neigh)  
            
    return G
        
        
        
G = get_graph_from_pandas(df)

print("Done.")
print("Total number of nodes: ", G.number_of_nodes())
print("Total number of edges: ", G.number_of_edges())

pos = nx.draw(G, with_labels=True, 
              node_color=[node[1]['colour'] for node in G.nodes(data=True)], 
              node_size=200)

给我一个 KeyError: 'colour'.

当我打印时

for node in G.nodes(data=True):     
     try:         
        node[1]['colour']     
     except KeyError:         
        print(node)

我明白了

('A', {}) 
('l', {}) 
('t', {}) 
('e', {})

你能解释一下是什么导致了这个错误吗？谢谢

更新：我认为错误来自这里

 for neigh in neighbors:
                #add edge weights here, attribute of G.add_edge
                G.add_edge(n,neigh)

Answer 1

df.Neighbors中的每一项都是一个字符串。当您使用 for neigh in neighbors: 对其进行迭代时，您将邻居的每个字符添加到该节点。例如第一个节点看起来像

>>> G.nodes
>>> NodeView(('Luke', 'A', 'l', 't', 'e'))

只要每行只有一个邻居，将for循环替换为

    # for neigh in neighbors:
    #     #add edge weights here, attribute of G.add_edge
    #     G.add_edge(n,neigh)  
    G.add_edge(n,neighbors)

尽管这并不能缓解 KeyError。

虽然 'John'、'Laura' 和 'Stella' 是邻居，但它们也是图中的节点，但它们是用 .add_edge 创建的，并且从来没有颜色分配给他们。

>>> for thing in G.nodes.items():
...     print(thing)
('Luke', {'weight': 3, 'colour': 'orange'})
('Alte', {'weight': 24, 'colour': 'blue'})
('John', {})
('Michael', {'weight': 43, 'colour': 'red'})
('Laura', {})
('Ludo', {'weight': 21, 'colour': 'orange'})
('Stella', {})

您可以在迭代之前先使用 default 属性添加这些节点：

...
    G.add_nodes_from(df.Neighbors,colour='white',weight=0)
    for row in df.itertuples(): # row is the row of the dataframe
        ...

如果您的节点属性可以以大写字母开头，则可以编写图形构造：

def get_graph_from_pandas(df):
    
    G = nx.DiGraph() # assuming the graph is directed since e.g node 1 has 
                     # 3 as neighbour but 3 doesnt have 1 as neighbour
    
    
    G.add_nodes_from(df.Neighbors,Colour='white',Weight=0)
    G.add_edges_from(df[['Node','Neighbors']].itertuples(index=False))
    dg = df.set_index('Node')
    G.add_nodes_from(dg[['Colour','Weight']].T.to_dict().items())
        
    return G

>>> for thing in G.nodes(data=True):
...     print(thing)
('Alte', {'Colour': 'blue', 'Weight': 24})
('John', {'Colour': 'white', 'Weight': 0})
('Laura', {'Colour': 'white', 'Weight': 0})
('Stella', {'Colour': 'white', 'Weight': 0})
('Ludo', {'Colour': 'orange', 'Weight': 21})
('Luke', {'Colour': 'orange', 'Weight': 3})
('Michael', {'Colour': 'red', 'Weight': 43})
>>> for thing in G.edges(data=True):
...     print(thing)
('Alte', 'Ludo', {})
('Alte', 'Luke', {})
('Ludo', 'Stella', {})
('Luke', 'Alte', {})
('Luke', 'John', {})
('Michael', 'Laura', {})

您可以直接从 G.nodes.items

获取节点颜色

pos = nx.draw(G, with_labels=True, 
              node_color=[d['Colour'] for n,d in G.nodes.items()], 
              node_size=200)

或nx.get_node_attributes

pos = nx.draw(G, with_labels=True, 
              node_color=nx.get_node_attributes(G,'Colour').values(),
              node_size=200)

Answer 2

二战答案解决了一个问题。

但是有一些问题需要解决：

只有Node栏中的节点会有颜色，只在Neighbors栏中引入的用户将在G.add_edge(n,neighbor)中创建，并且不会分配颜色。您需要决定为这些节点设置哪种颜色。
您要分配给边的权重正在分配给节点。

df = pd.DataFrame(  data = {"Node": ["Luke", "Luke", "Michael", "Ludo", "Alte", "Alte"],
                            "Neighbors": ["Ludo", "John", "Laura", "Stella", "Ludo", "Luke"],
                            "Colour": ["orange", "orange", "red", "orange", "blue", "blue"], 
                            "Weight": [3, 3 ,43, 21, 24, 24] 
                        }
              )
   

NROWS = None
def get_graph_from_pandas(df, v = False):
    
    G = nx.DiGraph() # assuming the graph is directed since e.g node 1 has 
                     # 3 as neighbour but 3 doesnt have 1 as neighbour
    
    for row in df.itertuples():
        print(row)
        n = row.Node
        w = row.Weight
        c = row.Colour
        neighbor = row.Neighbors
        
        G.add_node(n, weight = w, colour = c) # only nodes in column Node will have color
                                              # users that are only introduced in Neighbors column dwont have column
        if neighbor not in G.nodes:
            G.add_node(neighbor, weight = w, colour = "yellow") # this will set the default color to yellow
        G.add_edge(n,neighbor, weight = w) # weight of edge
            
    return G
        
G = get_graph_from_pandas(df, v = False)

print("Done.")
print("Total number of nodes: ", graph.number_of_nodes())
print("Total number of edges: ", graph.number_of_edges())

fig = plt.figure(figsize=(2,2))

pos = nx.draw(G, with_labels=True, 
              node_color=[node[1]['colour'] for node in G.nodes(data=True)], 
              node_size=200)

for node in G.nodes(data=True):
    try:
        node[1]['colour']
    except KeyError:
        print(node)

为节点分配颜色时出现 KeyError

KeyError when assign colours to nodes

python

networkx