Best approach in making instance of a class when __init__ takes a lot of time?

I'm currently working on somekind of device handler. The idea is to use Observer design pattern.

Let's say for example you as a 'user' want to add a new device for everyone else to use and would be globally avaiable in scope of the program.

What I wanted to do is implement DeviceHandler base class which will be marked as singleton using decorator. There would be 3 publicly visible methods register, unregister and get_device_list.

Also I wanted to implement a base class Device which you as a 'user' must inherit in order that your 'device' can be registered. Using abc.ABCMeta and abc.abstractmethod I would force your class to implement 2 functions get_instance() and find_me(). find_me() returns either True or False (depending if your device is connected to the system or not), get_instance() returns obviously instance of your class.

When an instance of DeviceHandler is created, in the __init__ method daemon thread is created which is running __discover method with 1 second period. __discover basicly calls find_me() method of registered device and if method returns True then get_instance() is called XY times until valid instance of your class is obtained (one call per iteration).

What the problem is that my DeviceHandler class expects your __init__ method to be non-blocking. When I call get_instance() I either expect an instance of your class or somekind of error code that would inform me that your class is not yet instantiated and that get_instance() needs to be called XY times until I get valid instance of your class (you could implement some kind of state-machine inside your class).

I wanted to find out what is better approach in acquiring instance of your class. Should I force you to implement get_instance() method and then you would implement state-machine handling (if needed) inside that method or should i just lose that method and instantiate your class as usually YourDeviceClass() and then you would implement state-maching handling in the __init__ method?