How do I write class objects to a file in binary mode?

[Exsul1]

How do I write class instances to a file in binary mode? When I try to run this code,

from npc_gen import NPC

n1 = NPC()


a = open("workfile", "wb")

a.write(n1)

a.close()

I'm told:

Output:
Unexpected type(s):
(NPC)

Possible types:
(bytearray)
(bytes)

How do I convert a (custom) class object into a bytes object? Pickle?

Also, is this the best way to do what I want to do? I'm making my first app. Users will want to save some of the custom class objects that are created to their phones. I figured I'd need to have the program create a separate file to store those objects in. Is this best practice?

(Apologies if I have used any terms incorrectly or misunderstood something fundamental. I'm still new to programming, so please use easy-to-understand explanations in your answers. Thank you!)