CODEWITHSUNDEEP
pythonnetworkx
Soutrik Mukherjee
Soutrik Mukherjee

Reputation: 25

g.nodes() from networkx is not working with random.choice()

I'm trying to generate random edges between random nodes but the line of code ab=choice(G.nodes()) is generating errors.

import networkx as nx
import matplotlib.pyplot as plt
from random import choice
G=nx.Graph()
city_set=['a','b','c','d','e','f','g','h']
for each in city_set:
    G.add_node(each)
ab=choice(G.nodes())
print(ab)

Errors

C:\Users\DELL\Anaconda2\envs\untitled\python.exe C:/Users/DELL/Documents/PythonPrograms/Beginning/ntwxproject.py Traceback (most recent call last): File "C:/Users/DELL/Documents/PythonPrograms/Beginning/ntwxproject.py", line 10, in ab=choice(G.nodes()) File "C:\Users\DELL\Anaconda2\envs\untitled\lib\random.py", line 259, in choice return seq[i] File "C:\Users\DELL\Anaconda2\envs\untitled\lib\site-packages\networkx\classes\reportviews.py", line 178, in getitem return self._nodes[n] KeyError: 1

Process finished with exit code 1

I'm new to python, help me with it.

Upvotes: 2

Views: 4261

Answers (3)

Soum
Soum

Reputation: 63

G.node usage is replaced by G.nodes from networkx version 2.4.

Hence you might come across this error if you are trying to un an old code which uses G.node as a key(s) identifier.

Replace all G.node with G.nodes or vice versa. depending on teh version you are trying to work.

enter image description here

Upvotes: 0

Yash Barapatre
Yash Barapatre

Reputation: 41

You can convert G.nodes() into a list format compatible with random.choice() by passing list(G.nodes()) instead of just G.nodes().

import networkx as nx
import matplotlib.pyplot as plt 
from random import choice      
G=nx.Graph()      
city_set=['a','b','c','d','e','f','g','h'] 
for each in city_set:     
    G.add_node(each)     
ab= choice(list(G.nodes())) 
print(ab)

Upvotes: 4

OBu
OBu

Reputation: 5177

Since it is not 100% clear what you want to do next, I try to give some hints on how to use random.choice() in combination with your city list (please note it's a "list", not a "set" - a better identifyer would be city_list).

Edit: I see you added some information - so I added a way to build the edges...

Your main problem is, that G.nodes() is a <class 'networkx.classes.reportviews.NodeView'>and not a simple list (even though its string representation looks like a list).

import networkx as nx 
import matplotlib.pyplot as plt 
import random 

G=nx.Graph() 
city_list=['a','b','c','d','e','f','g','h']

# this is a bit easier then adding each node in a loop 
G.add_nodes_from(city_list)

# show type and content of G.nodes() 
print(G.nodes())
print(type(G.nodes()))

# based on your old code:    
for _ in city_list: 
    ab=random.choice(city_list) 
    print(ab)
print("list is now", city_list)

# generate n random edges
n=5
for _ in range(n):
    # random.sample(city_list, 2) gives a 2-tuple from city list
    # The '*'-operator unpacks the tuple to two input values for the .add_edge() method
    G.add_edge(*random.sample(city_list, 2))
print("Edges generated:", G.edges())

I hope this helps a bit...

Upvotes: 0

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