why () is () and [] is [] work in other way?

[Steven D'Aprano]

On Wed, 25 Apr 2012 13:42:31 +0200, Thomas Rachel wrote:

> Two objects can be equal (=) without being identical (≡), but not the
> other way.


>>> x = float('nan')
>>> y = x
>>> x is y
True
>>> x == y
False


By the way, in mathematics, ≡ normally means "is equivalent to", which is 
not quite the same as "identical to".

http://mathworld.wolfram.com/Equivalent.html



-- 
Steven