The `@classmethod` decorator

Although most methods are tied to an object instance, it can sometimes be useful to create a method that does something with the class itself. To achieve this in Python, you can use the @classmethod decorator. This is often used to provide alternative constructors for a class.

For example, you may be writing a class that takes some magic token (like an API key) as a constructor argument, but you sometimes read this token from a configuration file. You could make use of a @classmethod to create an alternate constructor for when you want to read from the configuration file.

class Bot:
    def __init__(self, token: str):
        self._token = token  

    def from_config(cls, config: dict) -> Bot:
        token = config['token']
        return cls(token)

# now we can create the bot instance like this
alternative_bot = Bot.from_config(default_config)

# but this still works, too
regular_bot = Bot("tokenstring")
This is just one of the many use cases of @classmethod. A more in-depth explanation can be found here.