if instance exists problem ..

[Steven D'Aprano]

On Thu, 18 Oct 2007 03:00:56 +0000, Steven D'Aprano wrote:

> On Wed, 17 Oct 2007 23:12:15 +0000, Paul Hankin wrote:
> 
>> 'if x' doesn't test if x exists, it tests if x when cast to a bool is
>> True.
> 
> To be pedantic:
> 
> Python doesn't have type casts. bool(x) doesn't cast x as a bool, it
> creates a brand new Boolean object from x.

Actually, to be even more pedantic, True and False are both singletons, 
and so bool() doesn't actually create a new Boolean object but reuses the 
existing ones.


-- 
Steven.