Re: Multiple inheritance: Interface problem workaround, please comment this

[Steven Bethard]

Axel Straschil wrote:
I solved all my problems for pythons multiple inheritance with this ng,
thaks to all again, but there is one think I still dislike:
class A(object):
	def __init__(self, a=None, **__eat): 
		print "A"
		super(A, self).__init__()
class B(object):

	def __init__(self, b=None, **__eat): 
		print "B"
		super(B, self).__init__()

class AB(A, B):
	def __init__(self, a=None, b=None): 
		super(AB, self).__init__(a=a, b=b)

ab = AB()
[snip]
 
My problem: If you make a coding mistake, and the mistake does not give
a runtime error becouse **__eat is a hungry evil beast, it would be very
hard to debug ... think of a wrong written parameter!
I also agree that this style is not pretty.  What are A and B in your 
real code?  I would suggest that rather than this architecture, you 
might do better to either:
   (1) make A or B a mixin class that doesn't need __init__ called, or
   (2) make class AB inherit from A and delegate to B (or vice versa)
For example:

py> class A(object):
...     def __init__(self, x):
...         self.x = x
...
py> class B(object):
...     def __init__(self, y):
...         self.y = y
...
py> class C(object):
...     def m(self):
...         return self.x, self.y
...
py> class ABC(A, C):
...     def __init__(self, x, y):
...         super(ABC, self).__init__(x)
...         self._b = B(y)
...     def __getattr__(self, name):
...         return getattr(self._b, name)
...
py> a = ABC(1, 2)
py> a.x
1
py> a.y
2
py> a.m()
(1, 2)
Note that A is the "true" superclass, B is delegated to, and C is just a 
mixin class.

STeVe
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