python:list.pop(0)在列表已满时给出索引错误

Question

因此，我正在尝试取回 n 商店的列表，以使他们成为邻居，然后在必要时，然后，在邻居的邻居中。以下是用于计算此列表的代码，称为位置。商店的编号为1到10。

在这种情况下，每个商店都有4个邻居。这种关系是在词典中随机设置的，称为邻居。

import random
shops = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
neighbours = {}
for i in shops:
    neighbours[i] = random.sample(shops, 4)
    while i in neighbours[i]:
        neighbours[i] = random.sample(shops, 4)
print (neighbours)
shop_zero = random.randrange(1,11)
locations = [shop_zero]
neighborhd = neighbours[locations[0]]
n=10
while len(locations) < n:
    if not neighborhd:
        print('if statement')
        neighborhd = neighbours[random.choice(locations)]
        print (neighborhd)
    print('while loop')
    ne = neighborhd.pop(0)
    if ne not in locations:
        locations.append(ne)
print (locations)

问题在于代码有时有时，但通常会给我一个索引错误：

IndexError: pop from empty list

对于感兴趣的人，以下是邻居字典的输出：

{1: [7, 5, 4, 9], 2: [5, 6, 3, 7], 3: [10, 8, 7, 6], 4: [7, 8, 10, 2], 5: [3, 6, 1, 9], 6: [5, 1, 10, 3], 7: [3, 8, 6, 2], 8: [10, 4, 9, 7], 9: [6, 5, 3, 2], 10: [3, 5, 8, 7]}

我已经添加了一些打印语句，以使工作示例更具信息性。正如我之前说的那样，它确实经常起作用，但主要是给出索引错误。请帮助？

P.S。我意识到，最终的列表并不总是会给我群集，而是从邻居到邻居的途径。这对我正在进行的项目很好。

Answer 1

基本上，您在neighborhd = neighbours[random.choice(locations)]中有问题。它还返回空列表。因此，您需要几乎没有改变。if neighborhd:到pop之前只检查它不是空列表。

 import random
shops = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
neighbours = {}
for i in shops:
    neighbours[i] = random.sample(shops, 4)
    while i in neighbours[i]:
        neighbours[i] = random.sample(shops, 4)
print (neighbours)
shop_zero = random.randrange(1,11)
locations = [shop_zero]
neighborhd = neighbours[locations[0]]
n=10
while len(locations) < n:
    if not neighborhd:
        print('if statement')
        neighborhd = neighbours[random.choice(locations)]
        print (neighborhd)
    print('while loop')
    if neighborhd:
        ne = neighborhd.pop(0)
        if ne not in locations:
            locations.append(ne)
print (locations)

Answer 2

我更改了您的代码帮助调试，您可以在下面看到。如果您运行此操作，则发现当异常抛出时，"邻居"词典将空列表作为某些值。这意味着可以将"邻居"从"邻居"中重新填充，因此仍然是空的。

import random
shops = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
neighbours = {}
for i in shops:
    neighbours[i] = random.sample(shops, 4)
    while i in neighbours[i]:
        neighbours[i] = random.sample(shops, 4)
print (neighbours)
shop_zero = random.randrange(1,11)
locations = [shop_zero]
neighborhd = neighbours[locations[0]]
n=10
while len(locations) < n:
    if not neighborhd:
        print('if statement')
        neighborhd = neighbours[random.choice(locations)]
        print (neighborhd)
    print('while loop')
    try:
        ne = neighborhd.pop(0)
    except IndexError:
        raise IndexError("Attempt to pop from neighborhd which has content %s, formed from neighbours which has content %s" % (neighborhd, neighbours))
    if ne not in locations:
        locations.append(ne)
print (locations)