[Python-Dev] Design question: call __del__ only after successful __init__?

[Barry A. Warsaw]

>>>>> "GvR" == Guido van Rossum <guido@python.org> writes:

    GvR> Now I have a choice to make.  If the class has an __init__,
    GvR> should I clear the flag only after __init__ succeeds?  This
    GvR> means that if __init__ raises an exception, __del__ is never
    GvR> called.  This is an incompatibility.  It's possible that
    GvR> someone has written code that relies on __del__ being called
    GvR> even when __init__ fails halfway, and then their code would
    GvR> break.

It reminds me of the separation between object allocation and
initialization in ObjC.  

    GvR> But it is just as likely that calling __del__ on a partially
    GvR> uninitialized object is a bad mistake, and I am doing all
    GvR> these cases a favor by not calling __del__ when __init__
    GvR> failed!

    GvR> Any opinions?  If nobody speaks up, I'll make the change.

I think you should set the flag right before you call __init__(),
i.e. after (nearly all) the C level initialization has occurred.
Here's why: your "favor" can easily be accomplished by Python
constructs in the __init__():

class MyBogo:
    def __init__(self):
	self.get_delified = 0
	do_sumtin_exceptional()
	self.get_delified = 1

    def __del__(self):
	if self.get_delified:
	    ah_sweet_release()

-Barry