Change python mro at runtime

Question

I\'ve found myself in an unusual situation where I need to change the MRO of a class at runtime.

The code:

class A(object):
    def __init__(self):
          


        

Answer 1

I'd like to point out a solution which is very specific to the example you present in your question, and therefor unlikely to help. (But in case it does help at all...)

You can bypass hello's polymorphism by defining it as a class member, instead of a method.

class B(A):
    def __init__(self):
        super(B, self).__init__()
        print "__init__ B"
        self.msg_str = "B"
        self.hello = lambda: print "%s hello" % self.msg_str
        self.hello()

(A remains unchanged).

This solution will break if:

• you subclass B and need to override hello in the subclass
• msg_str is modified after __init__ runs
• probably several other cases...