[Python-Dev] PEP 289 - Generator Expressions - Let's Move Forward

[Edward Loper]

> Hello Guido,
> 
> I did a quick review of the stdlib, including the tests, to see which list
> comprehensions could be replaced with generator expressions.  Thought I admit
> I am biased towards early binding, I ended up looking for cases with the
> following properties:  [...]

Even if we switched to early binding, won't these issues still bite you 
with mutable values?  E.g.:

     some_dict = {'x': 1, 'y': 2}
     iter1 = (some_dict.get(v, 3) for v in input1)
     some_dict['z'] = 5
     iter2 = (some_dict.get(v, 7) for v in input2)

It seems like it would be surprising (to me, anyway) if this gave a 
different result than:

     some_dict = {'x': 1, 'y': 2}
     iter1 = (some_dict.get(v, 3) for v in input1)
     some_dict = {'x': 1, 'y': 2, 'z': 5}
     iter2 = (some_dict.get(v, 7) for v in input2)

-Edward