How to Change a Class Instance's Method in Python?

Question

I want to create a python library and part of the function of this library involves creating a class instance with some user defined variables. How do I let the user write their own conditionals for the class instance in said instance's method? For example, say I have an instance of the following class:

class Test:
    def __init__(self, some_value):
        self.some_value = some_value
    def func(self):
        pass

instance = Test(4)

How do I let a user change what instance.func() does (how can I let a user access the object's variables?

jackal · Accepted Answer · 2022-06-23 07:15:11Z

1

You could pass a reference to the user's function to init For example:

class Test:
    def __init__(self, user_function):
        self._function = user_function
    def func(self):
        return self._function()

def ufunc_1():
    return 'Hello world!'

def ufunc_2():
    return 'Goodbye cruel world'


t_1 = Test(ufunc_1)
t_2 = Test(ufunc_2)

print(t_1.func())
print(t_2.func())

In this way, the reference to the user function is stored in an instance variable.

Output:

Hello world!
Goodbye cruel world

answered Jun 23, 2022 at 7:15

jackal

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3 Comments

okayatcp12 Over a year ago

This works for me thank you. Are there any downsides to passing a non-local function to init (in the context of a public python library)?

okayatcp12 Over a year ago

Also, can the user-created functions access an instances variables?

jackal Over a year ago

@okayatcp12 The functions ufunc_1 and ufunc_2 could access instance variables of the Test class merely by passing a reference to the appropriate instance as a parameter

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