python - 如何在python中删除一个类

Question

如果无法重新启动 python 进程，如何删除或更新类？例如像下面这样:

代码是:

# coding:utf8


class A(object):

    value = 1


class B(A):

    value = 1


subclasses = A.__subclasses__()
print(subclasses)
for subclass in subclasses:
    print('{}:{}'.format(subclass, subclass.value))
print('')


class B(A):

    value = 2


subclasses = A.__subclasses__()
print(subclasses)
for subclass in subclasses:
    print('{}:{}'.format(subclass, subclass.value))
print('')

输出是:

[<class '__main__.B'>]
<class '__main__.B'>:1

[<class '__main__.B'>, <class '__main__.B'>]
<class '__main__.B'>:1
<class '__main__.B'>:2

如何删除第一个B类，让输出变为:

[<class '__main__.B'>]
<class '__main__.B'>:1

[<class '__main__.B'>]
<class '__main__.B'>:2

Answer 1

您可以使用 del和 gc删除子类然后垃圾收集:

class A(object):

    def __init__(self):
        a = 1

class B(A):

    def __init__(self):
        b = 1


subclasses = A.__subclasses__()
print(subclasses)


class B(A):

    def __init__(self):
        b = 2

del B
import gc
gc.collect()

subclasses = A.__subclasses__()
print(subclasses)

输出:

[<class '__main__.B'>]
[<class '__main__.B'>]