How to delete a class in python

Question

If you cannot restart a python process, how can you delete or update a class? For example like below:

The code is:

# 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('')

The output is:

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

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

How can I delete the first B class, let the output change to:

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

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

Can you re-define class A and then define B with the new definition? — Jano
– Jano, Commented Feb 28, 2020 at 8:06

Jamin · Accepted Answer · 2020-02-28 08:23:14Z

3

You can use del and gc to delete the subclass and then garbage collect:

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)

Output:

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

answered Feb 28, 2020 at 8:23

Jamin

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1 Comment

qux Over a year ago

Maybe you delete the second B class. I update the decription of the question.

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