Dynamically set inheritance in Python

Question

I have class A that is supposed to inherit class B whose name is not yet known at the time of A being written. Is it possible to declare A not inheriting anything, and add B as the base class during A's instantiation? Example:

First file

class B:
 def __init__(self):
 self.__name = "Class B"
 def name(self):
 return self.__name

Second file

class A:
 def __init__(self):
 self.__name = "Class A"
# At some point here, the appropriate module name and location is discovered
import sys
sys.path.append(CustomModulePath)
B = __import__(CustomModuleName)
magic(A, B) # TODO What should magic() do?
a = A()
print a.name() # This will now print "Class A", since name() is defined in B.

• danben: Can you explain why you need to do this?
• dpq: In this application I need to manipulate classes based on the application-specific metadata, not by regular class names.

Answer 1

Yeah, you can accomplish this with metaclasses. It's not the easiest topic to wrap your head around but it'll do the job. There's a Stack Overflow question about them that looks like it has some good information and I also found an IBM article that might help as well. Somewhere in the official Python documentation, there's a section about them but I can't recall exactly where offhand.

• Claudiu: the SO question particularly has an example on how to mess with inheritance, so look there for sure
• dpq: Looks like metaclasses are exactly what I needed, thanks a lot!