How to implement a sole class of methods inside an external class-CodePudding

I have an external class to represent my data idk. Inside the class idk I want to have another class change which will contain various methods to change instances of the class idk. What I've tried is below. Note: this is a simplified example of my actual code

class idk:
  def __init__(self):
    self.x=1
    self.y=2
  class change:
    def func(self):
      self.x=10
      self.y=100

var=idk()
var.change.func()
print(var.x, var.y)

However this gives the error: TypeError: func() missing 1 required positional argument 'self'

How do I change the code to make it work?

CodePudding user response：

Well, first of all, your are getting this error because you are accessing the func function as a class attribute and not by an instance of it (putting a class definition inside another class won't make it an instance).

If it makes sense, you cloud put those "change methods" in the idk class directly (that would be a normal approach):

class idk:
    def __init__(self):
        self.x = 1
        self.y = 2
  
    def func(self):
        self.x = 10
        self.y = 100

var = idk()
var.func()
print(var.x, var.y)  # Output: 10 100

If you really want/need to separate those methods, you could do another class. The way I would implement that class is with static methods where all of them recieve an idk instance as the first parameter:

class idk:
    def __init__(self):
        self.x = 1
        self.y = 2

class idkChanger:
    @staticmethod
    def func(idk_obj):
        idk_obj.x = 10
        idk_obj.y = 100

var = idk()
idkChanger.func(var)
print(var.x, var.y)  # Output: 10 100

If you really really want/need to have that "changer" class inside of the idk class you can define it there, but this is not common at all. Also, you will have to pass the instance as well, that Changer class:

class idk:
    def __init__(self):
        self.x = 1
        self.y = 2

    class Changer:
        @staticmethod
        def func(idk_obj):
            idk_obj.x = 10
            idk_obj.y = 100

var = idk()
idk.Changer.func(var)
print(var.x, var.y)  # Output: 10 100

Final notes:

You could not mark (decorate) the func as static and it will work the same, but this will bring more confution for several reasons (e.g., you would tecnically saying that func is an instance method. Which is not, because the objects you want to change are not Change's instances but idk's).