moving methods from class to instance of other class

[Terry Reedy]

On 6/28/2012 2:59 AM, lars van gemerden wrote:

> class A(object):
>      def __init__(self):
>          self.name = 'a'
>      def do(self):
>          print 'A.do: self.name =', self.name
>
> class B(object):
>      def __init__(self):
>          self.name = 'b'
>
> The question is: How do i move the 'do' method from A to b
 > (resulting in  printing "A.do: self.name = b")?

If you want to move the method from class A to class B
(which is normally more sensible than to instance b of B)

B.do = A.do.im_func  # Python 2
B.do = A.do  # Python 3
b = B()
b.do()
# print (with print adjusted for PY3)
A.do: self.name = b

If you want a B instance to act like an A instance, you can change its 
class (subject to some limitations). The following works.

b = B()
b.__class__ = A
b.do()

If make the change temporary and the reversion automatic, write a 
context manager.

-- 
Terry Jan Reedy