在 Python 中限制对象创建的程序

问题描述

class object_restrict(object):
    _count = 0

    def __new__(cls):
        if cls._count > 5:
            raise TypeError("Too many keys created")

        cls._count += 1
        print "object created"

    def __init__(self):
        pass

k = object_restrict()
k1 = object_restrict()
k2 = object_restrict()
k3 = object_restrict()
k4 = object_restrict()
k5 = object_restrict()

我似乎对如何在 Python 中限制类的对象数量有一些疑问.我被要求编写一个程序，我应该将条件放在我们只能创建一个类的 5 个实例的位置，如果我们尝试创建超过 5 个，它应该引发异常.

It seems I have some questions regarding how can we restrict the number of objects for a class in Python. I have been asked to write a program where I should put the condition where we can create only 5 instances of a class, and if we try to create more than 5, it should raise an exception.

正如我们在 Python 中所知，__new__ 是在需要创建实例时调用的方法.我试图写一些代码，但没有奏效.

As we know in Python, __new__ is the method which is get called whenever an instance needs to be created. I tried to write some code, but it didn't work.

当我运行这段代码时，它总共运行了 6 次.请问有人可以在这里指导我吗?我也试过在谷歌上检查，但没有得到任何正确的代码.

When I ran this code, it ran for all 6 times. Please can somebody guide me here? I also tried checking on Google but didn't get any proper code.

推荐答案

class object_restrict(object):
    _count = 0

    def __new__(cls):
        cls._count += 1
        if cls._count > 5:
            raise TypeError("Too many keys created")

        print cls._count, "object created"

    def __init__(self):
        pass

k = object_restrict()
k1 = object_restrict()
k2 = object_restrict()
k3 = object_restrict()
k4 = object_restrict()
k5 = object_restrict()

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