[Python] KeyError in nx.algorithms.approximation.traveling_salesman_problem()

I have written a code which generates 10 random graphs and solve the traveling salesman problem using NetworkX. I am getting KeyError: 1.

Following is my code.

import networkx as nx
import matplotlib.pyplot as plt
import numpy as np
import time
import csv
import pandas as pd

# Function to generate a random graph
def generate_random_graph(num_nodes, edge_prob):
return nx.erdos_renyi_graph(num_nodes, edge_prob)

# Function to solve TSP and track time
def solve_tsp(graph):
start_time = time.time()
cycle = nx.algorithms.approximation.traveling_salesman_problem(graph, cycle=True)
end_time = time.time()
elapsed_time = end_time - start_time
return cycle, elapsed_time

# Number of nodes in the graph
num_nodes = 10

data_points = []
csv_data = []

# Generate 10 random graphs, solve TSP, and record data
for i in range(10):
edge_prob = np.random.rand() # Random edge probability
graph = generate_random_graph(num_nodes, edge_prob)
density = nx.density(graph)

# Solve TSP
cycle, elapsed_time = solve_tsp(graph)

# Record data
data_points.append((density, elapsed_time))

# Prepare adjacency matrix for CSV
adj_matrix = nx.adjacency_matrix(graph).todense().tolist()

csv_data.append([adj_matrix, density, elapsed_time, cycle])


I am getting the following error:

KeyError Traceback (most recent call last)
Cell In[7], line 8
5 density = nx.density(graph)
7 # Solve TSP
----> 8 cycle, elapsed_time = solve_tsp(graph)
10 # Record data
11 data_points.append((density, elapsed_time))

Cell In[3], line 4, in solve_tsp(graph)
2 def solve_tsp(graph):
3 start_time = time.time()
----> 4 cycle = nx.algorithms.approximation.traveling_salesman_problem(graph, cycle=True)
5 end_time = time.time()
6 elapsed_time = end_time - start_time

File ~/anaconda3/envs/py39/lib/python3.9/site-packages/networkx/utils/backends.py:412, in _dispatch.__call__(self, backend, *args, **kwargs)
409 def __call__(self, /, *args, backend=None, **kwargs):
410 if not backends:
411 # Fast path if no backends are installed
--> 412 return self.orig_func(*args, **kwargs)
414 # Use `backend_name` in this function instead of `backend`
415 backend_name = backend

File ~/anaconda3/envs/py39/lib/python3.9/site-packages/networkx/algorithms/approximation/traveling_salesman.py:320, in traveling_salesman_problem(G, weight, nodes, cycle, method)
318 if u == v:
319 continue
--> 320 GG.add_edge(u, v, weight=dist[v])
321 best_GG = method(GG, weight)
323 if not cycle:
324 # find and remove the biggest edge

KeyError: 1


How can I resolve it?

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