Comparison with False - something I don't understand

[Harishankar]

On Thu, 02 Dec 2010 00:15:42 -0800, Alice Bevan–McGregor wrote:

> Howdy!

Good day to you! 

> (False == 0) is True
> (True == 1) is True

I see. Thanks for this. I suspected this, but wasn't sure.

> The bool type is a subclass of int!  (Run those lines in a Python
> interpreter to see.  ;)
> 
>> if var == False:
> 
> if var is False: …

So "var is False" is safer to use when I want to specifically check 
whether var is set to False and not 0 or None?

> If you want to check not just for value equivelance (False == 0) but
> literal type, use the "is" comparator.  "is" checks, and others correct
> me if I'm wrong, the literal memory address of an object against
> another.  E.g. False, being a singleton, will always have the same
> memory address.  (This is true of CPython, possibly not of Python
> implementations like Jython or IronPython.)  Using "is" will be
> effective for checking for literal None as well.

Thanks, it makes sense to me now. Literal equivalence is what I was 
looking for. I didn't quite understand whether == achieved this or not. 
Now I guess I know. 

> 
> When ever I need to test for None, I always use the "is" comparator.
> It's also more English-like.  (None, evaluating to False when using
> '==', is useful when all you care about is having a blank default value,
> for example.)

Yes, but in my function I don't want to confuse False with 0 or anything 
else except False. Thanks again for explaining this clearly.
-- 
Harishankar (http://harishankar.org http://lawstudentscommunity.com)