python - 函数给出错误 ValueError: list.remove(x): x not in list

问题描述

我正在制作一个寻找最近的房子和房子清单的程序。这 3 个函数用于查找课程，当我去打印结果时，最后给了我错误：

File "C:/Users/ASUS/.spyder-py3/tp_1.py", line 88, in percurso
  Casas.remove(pos_i)

ValueError: list.remove(x): x not in list

def distancia_casas(P1, P2):
    "returns distance between points"
    delta_x = P2[0] - P1[0]
    delta_y = P2[1] - P1[1]
    distance = ((delta_x ** 2) + (delta_y ** 2)) ** 0.5
    return distance

def casa_mais_proxima(P, Casas):

    pos_inicial = Casas[0]
    pos_mini = (len(Casas), len(Casas))
    dist_mini = distancia_casas(P, pos_mini)

    for c in Casas:
        dist = distancia_casas(P, c)

        if dist < dist_mini:
            pos_mini = c
            dist_mini = dist

        elif dist == dist_mini and pos_inicial[0] > c[0]:
            pos_mini = pos_inicial

        elif dist == dist_mini and pos_inicial[0] < c[0]:
            pos_mini = c

        elif dist == dist_mini and pos_inicial[0] == c[0] and pos_inicial[1] > c[1]:
            pos_mini = pos_inicial

        elif dist == dist_mini and pos_inicial[0] == c[0] and pos_inicial[1] < c[1]:
            pos_mini = c

        elif dist >  dist_mini:
            pos_mini = pos_mini

        else:
            pos_mini = c

    return pos_mini

def percurso(Inicial, Casas):

    pos_i = Inicial

    course = [pos_i,]

    n = len(Casas) - 1

    for c in range(n):
        print(pos_i, Casas)

        pos_i = casa_mais_proxima(pos_i, Casas)

        Casas.remove(pos_i)

        course.append(pos_i)

    if (len(Casas) - 1) != 0:

        course.append(Casas[0])

    return course

print("percurso", percurso((3,2),[(0,1),(1,0),(1,2),(2,3)]))

谁能帮我？我已经打了 3 天了，但一无所获

标签： python

您不应该在迭代列表时从列表中删除项目。正如错误消息所述，您正在尝试删除不存在的元素。所以：

您可以使用列表推导创建一个仅包含您要删除的元素的新列表：

no_casas = []
for c in range(n):
    print(pos_i, Casas)

    pos_i = casa_mais_proxima(pos_i, Casas)

    no_casas.append(pos_i)

    course.append(pos_i)

for item in no_casas:
    Casas.remove(item)

但是，这种方法也会导致相同的异常，因为可以多次casa_mais_proxima返回相同的元素（这是该函数的预期行为吗？）Casa

所以：

您可以使用Try / Except ValueError：

try:
    Casas.remove(pos_i)
    course.append(pos_i)


except ValueError:
    print(str(pos_i) + " not in Casas")

输出：

(3, 2) [(0, 1), (1, 0), (1, 2), (2, 3)]
(2, 3) [(0, 1), (1, 0), (1, 2)]
(3, 3) not in Casas
(3, 3) [(0, 1), (1, 0), (1, 2)]
(3, 3) not in Casas
percurso [(3, 2), (2, 3), (2, 3), (3, 3), (3, 3), (0, 1)]

python - 函数给出错误 ValueError: list.remove(x): x not in list

问题描述

解决方案

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