使 dijkstra 算法从 python 中的 .txt 文件中获取输入

Question

i'm trying to make this dijkstra algorithm take input for "testedges' from a text file (vertices.txt) so I want 'testedges = myedges' to work without errors. and make the user enters the two vertices that he wants to know the shortest path between, so I need to use input() and don't manually write the two nodes in the code like it's shown below in the full code.

The full code:

from collections import defaultdict
from heapq import *

def dijkstra(edges, f, t):
  

    return float("inf")
if __name__ == "__main__":
    testedges = [
        ("A", "B", 7),
        ("A", "D", 5),
        ("B", "C", 8),
        ("B", "D", 9),
        ("B", "E", 7),
        ("C", "E", 5),
        ("D", "E", 15),
        ("D", "F", 6),
        ("E", "F", 8),
        ("E", "G", 9),
        ("F", "G", 11)
    ]

    print("=== Dijkstra ===")
    print (testedges)
    print ("A -> E:")
    print (dijkstra(testedges, 'A', 'E'))
    print ("F -> G:")
    print (dijkstra(testedges, "F", "G"))

the adjustment I want are:

testedges = myedges        # meanning that I want the edges to come straight from the .txt file 
print (input() ,"->" ,input()) # get the shortest path for the two nodes user chooses
 print (dijkstra(myedges, input(), input()) 

.txt is formatted this way

4,3,10 // i, j, k tells you that there is an edge between vi and vj and its 
          weight is k.
2,1,4  // v1,v2,5 and so on for the rest 
1,3,2
3,4,3
0,2,30

note:

Answer 1

For file which contains edges like:

A,B,7
C,D,8
... 

You can do something like:

# 1. Reading edge info from the file 
with open("vertices.txt") as f:
    lines = f.readlines()
    # store ordered pair of node 1, node2 and integer distance in a list
    my_edges = []
    for line in lines:
        node1, node2, distance = (line.strip().split(','))
        my_edges.append((node1,node2, int(distance)))
# similarly you can read other information like coordinates.

test_edges = my_edges

# 2. taking string input from user. 
# As input required is string, we don't need to typecast
print("Enter start node")
start_node = input()
print("Enter end node")
end_node = input()

# 3. call function that returns shortest path
shortest_path = dijkstra(test_edges, start_node, end_node)

Some general advice:

• Use descriptive, readable variable names (eg not myarray)
• read python docs for standard functionality that Python provides for strings and files ( split() , strip() , input() and open() ). It allows you to do more in less lines of code and has nice examples of doing such things.

Answer 2

A possible solution is:

A configuration file, named dijkstra.config , having the following content:

[PARAMETERS]
node_numbers: 5
coordinates: (1, 10),(8, 10),(10, 8),(7, 4),(3, 1)
nodes: (0,1,10),(1,2,5),(2,3,25),(0,3,3),(3,4,8)

You can check how to use it running in a python file test.py the following code:

import configparser

config = configparser.ConfigParser()
config.read("dijkstra.config")

print("number of nodes:\n" ,config["PARAMETERS"]["node_numbers"])
print("coordinates:\n", config["PARAMETERS"]["coordinates"])
print("nodes:\n", config["PARAMETERS"]["nodes"])