python - 类型错误 : argument of type 'instance' is not iterable

Question

这是我的代码，它在行处中断:

 if (suc not in sFrontier) or (suc not in sExplored):

报错:TypeError: argument of type 'instance' is not iterable

 """
    The pseudocode I'm following
initialize the frontier using the initial state of the problem
initialize the explored set to be empty
loop do
    if the frontier is empty then return failure
    choose a leaf node and remove it from the frontier
    if the node contains a goal state then return the corresponding solution
    add the node to the explored set
    expand the chosen node, adding the resulting nodes to the frontier
        only if not in the frontier or explored set
"""

sFrontier = util.Stack()
sFrontier.push(problem.getStartState())
sExplored = util.Stack()
lSuccessors = []

while not sFrontier.isEmpty():
  leaf = sFrontier.pop()

  if problem.isGoalState(leaf):
    solution = []
    while not sExplored.isEmpty():
      solution[:0] = (sExplored.pop())[2]
      return solution
  sExplored.push(leaf)
  lSuccessors = problem.getSuccessors(leaf)
  for suc in lSuccessors:
      if (suc not in sFrontier) or (suc not in sExplored):
        sFrontier.push(suc)
return []

problem.getSuccessors 返回后继状态列表、它们需要的操作以及 1 的成本。

之后

lSuccessors = problem.getSuccessors(leaf)

l后继者打印

  [((5,4), 'South', 1), ((4,5), 'West', 1)]

及之后

  for suc in lSuccessors:

成功打印

  ((5,4), 'South', 1)

为什么会坏？是因为sFrontier和sExplored是栈，不能在栈中查找吗？

我需要一个 contain() 方法还是只使用一个列表？

感谢所有帮助:)

Answer 1

如果您的堆栈不支持包含测试，它确实会抛出错误。您需要添加一个 __contains__ method给他们以支持 in 测试。

in 测试可以通过其他方式在您的堆栈中找到项目，但不推荐使用它们，因为它们的效率不如 __contains__ 方法；查看in expression documentation .