Question

I know with getattr() you can call the method, but I need to overwrite it, so myInstance.mymethod will be overwritten.

I have the method’s name as a string and the instance’s reference.

Answer 1

You can overwrite it with setattr

>>> class Foo(object):
...    def method(self): pass
... 
>>> a = Foo()
>>> a.method()
>>> setattr(a,'method',1)
>>> a.method()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not callable

To replace with another method:

>>> import types
>>> setattr(a,'method',types.MethodType(lambda self: self.__class__.__name__,a))
>>> a.method()
'Foo'

Where the lambda stuff is just fancy shorthand for defining a function:

def func(self):
    return self.__class__.__name__

setattr(a,'method',types.MethodType(func,a))