Is it safe to replace a self object by another object of the same type in a method ?

Question

I would like to replace an object instance by another instance inside a method like this:

class A:
    def method1(self):
        self = func(self)

The object is retrieved from a database.

Answer 1

Yes, all that will happen is that you won't be able to reference the current instance of your class A (unless you set another variable to self before you change it.) I wouldn't recommend it though, it makes for less readable code.

Note that you're only changing a variable, just like any other. Doing self = 123 is the same as doing abc = 123. self is only a reference to the current instance within the method. You can't change your instance by setting self.

What func(self) should do is to change the variables of your instance:

def func(obj):
    obj.var_a = 123
    obj.var_b = 'abc'

Then do this:

class A:
    def method1(self):
        func(self) # No need to assign self here

Answer 2

It is unlikely that replacing the 'self' variable will accomplish whatever you're trying to do, that couldn't just be accomplished by storing the result of func(self) in a different variable. 'self' is effectively a local variable only defined for the duration of the method call, used to pass in the instance of the class which is being operated upon. Replacing self will not actually replace references to the original instance of the class held by other objects, nor will it create a lasting reference to the new instance which was assigned to it.