Question

我正在尝试在Python中的文件中输出结果但是它既不工作也不显示任何错误。

以下是我的代码：

from collections import namedtuple
from pprint import pprint as pp

final_data = []
inf = float('inf')
Edge = namedtuple('Edge', 'start, end, cost')
class Graph():
def __init__(self, edges):
    self.edges = edges2 = [Edge(*edge) for edge in edges]
    self.vertices = set(sum(([e.start, e.end] for e in edges2), []))

def dijkstra(self, source, dest):
    assert source in self.vertices
    dist = {vertex: inf for vertex in self.vertices}
    previous = {vertex: None for vertex in self.vertices}
    dist[source] = 0
    q = self.vertices.copy()
    neighbours = {vertex: set() for vertex in self.vertices}
    for start, end, cost in self.edges:
        neighbours[start].add((end, cost))
    #pp(neighbours)

    while q:
        u = min(q, key=lambda vertex: dist[vertex])
        q.remove(u)
        if dist[u] == inf or u == dest:
            break
        for v, cost in neighbours[u]:
            alt = dist[u] + cost
            if alt < dist[v]:                                  
                dist[v] = alt
                previous[v] = u
    #pp(previous)
    s, u = [], dest
    while previous[u]:
        s.insert(0, u)
        u = previous[u]
    s.insert(0, u)
    return s

start_point = input('Enter the starting point: ') 
end_point = input('Enter the ending point: ')
file_name = input('Enter the input file name: ')
output_file = input('Enter the output file name: ')
f = open(file_name, 'r')

data = f.readlines()

for line in data:
    f_line = line
    values = f_line.split()
    values[2] = int(values[2])
    final_data.append(values)

graph = Graph(final_data)




f = open(output_file, 'a')

result = str(pp(graph.dijkstra(start_point, end_point)))
f.write(result)

注意：忽略缩进

我不确定我到底在哪里弄错了。我尝试使用append（a）和write（w）写入文件，但两者都不起作用。文件的所有路径都是正确的，输入文件读取完好，输出文件也在同一个文件夹中。

Answer 1

f = open(output_file, 'a')
result = str(pp(graph.dijkstra(start_point, end_point)))
f.write(result)

你要改为：

with open(output_file, 'a') as f:
    result = pprint.pformat(graph.dijkstra(start_point, end_point))
    f.write(result)

因为pprint.pprint()是print的替代，因此具有相同的“原型”，不会返回任何内容。 pprint.pformat已被制作，因此您可以“打印”到字符串。虽然，你可能想做

with open(output_file, 'a') as f:
    pp(graph.dijkstra(start_point, end_point), stream=f)

作为pprint的帮助：

Help on function pprint in module pprint:

pprint(object, stream=None, indent=1, width=80, depth=None)
    Pretty-print a Python object to a stream [default is sys.stdout].

将输出写入文件不起作用：未找到错误

1 个答案: