问题
I am getting a KeyError when I try to create a network.
My dataset is
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
The table above shows the links by nodes:
- node Luke is linked with Alte and John. It has edge weight 3 and colour orange
- node Michael is linked with Laura. It has weight 43 and colour red
- node Ludo is linked with Stella. It has weight 21 and colour orange
- node Alte is linked with Luke and Ludo. It has colour blue and weight 24
Doing as follows:
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)
gives me a KeyError: 'colour'.
When I print
for node in G.nodes(data=True):
try:
node[1]['colour']
except KeyError:
print(node)
I get
('A', {})
('l', {})
('t', {})
('e', {})
Can you please explain what is causing the error? Thanks
Update: I think the error is from here
for neigh in neighbors:
#add edge weights here, attribute of G.add_edge
G.add_edge(n,neigh)
回答1:
wwii answer solves one problem.
However there are a number of problems that need to be fixed:
Only nodes in column Node will have color, users that are only introduced in Neighbors column will be created in
G.add_edge(n,neighbor), and won't have a color assigned. You need to decide which color to set for these nodes.The weight you want to attribute to the edges is being attributed to the nodes.
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)
回答2:
Each item in df.Neighbors is a string. When you iterate over it with for neigh in neighbors: You add each character of the neighbor to the node. For example the first node looks like
>>> G.nodes
>>> NodeView(('Luke', 'A', 'l', 't', 'e'))
As long as each row only has a single Neighbor, replace the for loop with
# for neigh in neighbors:
# #add edge weights here, attribute of G.add_edge
# G.add_edge(n,neigh)
G.add_edge(n,neighbors)
Although this doesn't alleviate the KeyError.
While 'John', 'Laura', and 'Stella' are neighbors they are also nodes in the graph but they were created with .add_edge and never had a color assigned to them.
>>> 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', {})
You can add those nodes first with default attributes before iterating:
...
G.add_nodes_from(df.Neighbors,colour='white',weight=0)
for row in df.itertuples(): # row is the row of the dataframe
...
If your node attributes can begin with capitals the graph construction could be written:
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', {})
You can get the node colors directly from G.nodes.items
pos = nx.draw(G, with_labels=True,
node_color=[d['Colour'] for n,d in G.nodes.items()],
node_size=200)
or nx.get_node_attributes
pos = nx.draw(G, with_labels=True,
node_color=nx.get_node_attributes(G,'Colour').values(),
node_size=200)
来源：https://stackoverflow.com/questions/65205566/keyerror-when-assign-colours-to-nodes