Question

我如何通过索引解决类实例？例如，如果我有

class Body(object):
    def __init__(self, attribute1, attribute2)
        self.attribute1 = attribute1
        self.attribute2 = attribute2

class1 = Body(1,2)
class2 = Body(3,4)

我希望能够做到这样的事情：

Body[1].attribute1

并返回值1.

Answer 1

您始终可以将实例放在列表中：

classes = [Body(1,2), Body(3,4)]

然后你可以索引列表：

>>> classes[0].attribute1   # attribute1 of the first element in the list
1

>>> classes[1].attribute2   # attribute2 of the second element in the list
4

请注意，索引以0而不是1开头。

顺便说一下，:之后你错过了def __init__(self, attribute1, attribute2)。

如果你真的想要你的行为，你可以使用元类来做（不推荐！）：

class IndexableClass(type):
    def __init__(self, *args):
        """Called when the class (not instances!) is created."""
        self._instances = []   # a class attribute keeping references to the instances

    def __getitem__(self, index):
        """Called when the class is indexed."""
        return self._instances[index]

    def __call__(self, *args, **kwargs):
        """Called when a new instance is created."""
        res = type.__call__(self, *args, **kwargs)
        self._instances.append(res)
        return res

class Body(object, metaclass=IndexableClass):
    def __init__(self, attribute1, attribute2):
        self.attribute1 = attribute1
        self.attribute2 = attribute2

class1 = Body(1,2)
class2 = Body(3,4)

Body[0].attribute1   # 1

Answer 2

您必须将它们放入某种类型的集合中，例如列表或元组。

class Body(object):
    def __init__(self, attribute1, attribute2)
        self.attribute1 = attribute1
        self.attribute2 = attribute2


class1 = Body(1,2)
class2 = Body(3,4)
bodies = [class1, class2]
bodies[1].attribute1

Answer 3

您可以列出类实例：

classes = [class1, class2]
print(classes[1].attribute1)

Answer 4

class Body(object):
    bodies = []
    def __init__(self, attribute1, attribute2)
        self.attribute1 = attribute1
        self.attribute2 = attribute2
        Body.bodies.append(self)

class1 = Body(1,2)
class2 = Body(3,4)
Body.bodies[0]
Body.bodies[1]

Bodies是静态列表。每次创建新的身体对象时，它都会自动将其自身添加到列表中。

如何通过索引来处理类实例

4 个答案: