Question about generators

[Frank Millman]

Hi all

This is purely academic, but I would like to understand the following -

 >>>
 >>> a = [('x', 'y')]
 >>>
 >>> s = []
 >>> for b, c in a:
...   s.append((b, c))
...
 >>> s
[('x', 'y')]


This is what I expected.

 >>>
 >>> s = []
 >>> s.append(((b, c) for b, c in a))
 >>> s
[<generator object <genexpr> at 0x0000019FC3F863C0>]
 >>>

I expected the same as the first one.

I understand the concept that a generator does not return a value until 
you call next() on it, but I have not grasped the essential difference 
between the above two constructions.

TIA for any insights.

Frank Millman