On Apr 22, 4:36 am, "Steven W. Orr" <[EMAIL PROTECTED]> wrote:
> When I go to create an object I want to be able to decide whether the
> object is valid or not in __init__, and if not, I want the constructor to
> return something other than an object, (like maybe None). I seem to be
> having problems. At the end of __init__ I say (something like)
>
> if self.something < minvalue:
> del self
> return None
>
> and it doesn't work. I first tried just the return None, then I got crafty
> and tried the del self. Is what I'm trying to do possible in the
> constructor or do I have to check after I return? Or would raising an
> exception in the constructor be appropriate?
You can raise an exception of course but it would just create a side
effect. Another way to achieve what you request for is manipulating
the class creation mechanism.
class A(object):
def __new__(cls, x):
if x == 0:
return None
obj = object.__new__(cls)
obj.__init__(x)
return obj
class B(A):
def __init__(self, x):
self.x = x
The condition can always be checked within the static __new__ method.
Kay
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