i = self._randbelow(len(seq)) TypeError: object of type 'NoneType' has no len()

Question

我在运行构建完美迷宫的代码时出现此错误。这是代码：

   def walk(self, s, x, y):

        neighboor = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]

        if s.size() == self.size**2: return

        else:

            while True:
                new = choice(neighboor)
                if self.is_valid(new[0], new[1]): break

            while self.maze[new[0]][new[1]].getVisit():

                if len(neighboor) != 0: new = choice(neighboor.remove(new))
                else:
                    temp = s.pop(s)
                    self.walk(s, temp[0], temp[1])

            #print(new)

            self.maze[new[0]][new[1]].changeVisit()
            if new == neighboor[1]:
                self.maze[x][y].changeNorth()
                self.maze[new[0]][new[1]].changeSouth()
            elif new == neighboor[0]:
                self.maze[x][y].changeSouth()
                self.maze[new[0]][new[1]].changeNorth()
            elif new == neighboor[2]:
                self.maze[x][y].changeEast()
                self.maze[new[0]][new[1]].changeWest()
            elif new == neighboor[3]:
                self.maze[x][y].changeWest()
                self.maze[new[0]][new[1]].changeEast()


            s.push(new)

            self.walk(s, new[0], new[1])

这是我得到的错误：

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    a.search()
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 93, in search
    self.walk(s, startX, startY)
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 76, in walk
    self.walk(s, new[0], new[1])
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 76, in walk
    self.walk(s, new[0], new[1])
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 76, in walk
    self.walk(s, new[0], new[1])
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 76, in walk
    self.walk(s, new[0], new[1])
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 76, in walk
    self.walk(s, new[0], new[1])
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 76, in walk
    self.walk(s, new[0], new[1])
  File "C:\Users\Serena\Desktop\XAproject\Stack.py", line 52, in walk
    if len(neighboor) != 0: new = choice(neighboor.remove(new))
  File "C:\Python34\lib\random.py", line 253, in choice
    i = self._randbelow(len(seq))
TypeError: object of type 'NoneType' has no len()

我认为'neighboor'是一个包含四组数字的列表，应该有len()。

我是编程新手，如有任何帮助，我们将不胜感激。

Answer 1

几件事。首先，如果您使用的是从通配符导入（来自随机导入 *）导入的 choice() 之类的东西，那么包含它会很有用，否则我们只是猜测您从哪里获得该函数。另外，wildcard imports are considered bad practice anyway.

问题是列表的 remove() 方法 returns None。您不能从 None 中选择某些内容，因为 None 不是可迭代的。也就是说 remove() 方法不支持链接。尝试更改：

if len(neighboor) != 0: new = choice(neighboor.remove(new)) # Passes None to choice() which raises an error

至

if len(neighboor) != 0:
    neighboor.remove(new) # removes the element from neighboor
    new = choice(neighboor) # Chooses from the list as you intended

您可能还有其他错误，但这是您发布的回溯错误。

为了将来，我建议您熟悉 Python 的回溯，因为它会准确地告诉您出了什么问题。 Here's a resource.

顺便说一句，你是指邻居而不是邻居吗？

i = self._randbelow(len(seq)) TypeError: object of type 'NoneType' has no len()

i = self._randbelow(len(seq)) TypeError: object of type 'NoneType' has no len()

python

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