iterator wrapper

[alf]

Simon Forman wrote:
>>
>>>|>> I = ([n] for n in i)
>>
>>This is nice but I am iterating thru hude objects (like MBs) so you know ...
>>
> 
> No, I don't know...  :-)

potentially my source lists are huge - so wanted to avoid unnecessary 
memory allocation


> My friend, I think you've misunderstood.  Observe:
> 
> |>> L = [n for n in range(3)]
> |>> G = (n for n in range(3))
> |>> L
> [0, 1, 2]
> |>> G
> <generator object at 0xb7d982ec>

well, I am in the python 2.3 word where generator comprehensions seem 
not to work. So I just took it a preallocated list comprehention. still 
wonder if there would be a difference between:

G = (n for n in range(300000000))  - this creates the huge list there
G = (n for n in xrange(300000000)) - this (at least to my understanding) 
  does not


> 
> List comprehensions [] create lists, generator comprehensions () create
> generators.
> 


> Generator comprehensions work "just-in-time", pulling items from
> whatever they're iterating over as they themselves are iterated over,
> as I hope this example makes clear:
> 
 >[...]

got it now ... thx or the lesson....


A.