can a class intantiate itself to None?

David Allen mda at idatar.com
Sat Mar 17 19:38:56 CET 2001


In article <mailman.984770427.21248.python-list at python.org>, "Timothy Grant"
<tjg at exceptionalminds.com> wrote:

> I'd like to create a class that can instantiate itself to None when
> instantiation fails...
> 
> class foo:
> 	def __init__(self, bar):
> 		if type(bar) == StringType:
> 				self.data = 'This is a String'
> 				
> 
> x = foo('a')
> 
> y = foo(1)  # In this instance I would like y to be None
> 
> So, can it be done, or do I need to raise an exception, catch it and then
> set y to None?

Raise an exception and set y to None.

You have the option of setting all class data to 
None if something doesn't happen that you want to 
happen, but there isn't a way that you can actually
return None from a constructor as far as I know of.
Besides, that would be confusing as hell, and that's
partially what exceptions are for, so use 'em.

-- 
David Allen
http://opop.nols.com/
----------------------------------------
Be wary of strong drink. It can make you shoot at tax collectors and 
miss 
- Lazarus Long, "Time Enough for Love"



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