I need a class function which creates a new instance from existing instance attributes.

This seems to me to be a factory function (hence the thought that it could be a classmethod), but it needs the class to be instanced.

Should/May I use the decorator @classmethod?

from dataclasses import dataclass

@dataclass
class Coin:
  obverse: str
  reverse: str

  def flip(self):
      return Coin(self.reverse, self.obverse)


cent = Coin('cent_ob', 'cent_rev')
flipped_cent = cent.flip()

cent
Out[20]: Coin(obverse='cent_ob', reverse='cent_rev')
flipped_cent
Out[21]: Coin(obverse='cent_rev', reverse='cent_ob')

This works.

But if I use the decorator @classmethod, it does not any longer.

from dataclasses import dataclass

@dataclass
class Coin:
  obverse: str
  reverse: str

  @classmethod
  def flip(cls, self):
      return cls(self.reverse, self.obverse)

cent = Coin('cent_ob', 'cent_rev')
flipped_cent = cent.flip()

TypeError: Coin.flip() missing 1 required positional argument: 'self'

Please, what case am i dealing with here?
Is there another decorator more suited to this case?

I believe that my primary goal is more to have a decorator explicitely indicating “hey, you have a factory function here”.

Thank you for your help!