使用列表时,'runtimeError:cmp'中超出了最大递归深度

Question

我在RuntimeError: maximum recursion depth exceeded in cmp使用列表时遇到了错误.更确切地说,p0 in points中,points.index(p0)方法调用,以及在points.remove(p0)上方法调用points列表已经提出了具体的字典中的错误p0在我的特定索引points列表.该points列表包含错误时的4700个词典,从12000个对象列表中将一个词典减少一个,直到出现错误.该p0字典包含对列表中另一个字典的引用,该字典在返回时包含对该p0对象的引用.该p0字典以及字典它包含一个参考的两次出现points由上述三种方法调用引发错误之前列表.

这个错误来自哪里？

编辑:这是引发错误的代码.

for roadType in roadTypes:
    points = roadPoints[roadType][:]

    while len(roadTails[roadType]) > 0:
        p0 = roadTails[roadType].pop()

        p1 = p0['next']
        points.remove(p0) # Where the error occurs
        points.remove(p1)

        while True:
            p2 = find(p1, points, 0.01)

            if p2:
                points.remove(p2)

                p3 = p2['next']
                points.remove(p3)

                if p3 in roadTails[roadType]:
                    roadTails[roadType].remove(p3)
                    break
                else:
                    p0, p1 = p2, p3
                    continue

            else: break

这是定义find,其中dist计算两点之间的距离.

def find(p1, points, tolerance = 0.01):
    for p2 in points:
        if dist(p2['coords'], p1['coords']) <= tolerance:
            return p2
    return False

这是错误的完整回溯:

Traceback (most recent call last):
  File "app.py", line 314, in <module>
    points.remove(p0) # Where the error occurs
RuntimeError: maximum recursion depth exceeded in cmp

Answer 1

可能你有一个循环结构,你的一个dicts通过一个'next's 链引用自己,如下所示:

>>> a = {}
>>> b = {}
>>> a['next'] = b
>>> b['next'] = a
>>> a == b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: maximum recursion depth exceeded in cmp

如果您打印出dict,循环引用将显示为...:

>>> a
{'next': {'next': {...}}}

也许这有助于找到字典中有问题的部分.