Best way to add a "position" value to each item in a list

[Sean]

I have a huge list, 10,000,000+ items.  Each item is a dictionary with
fields used to sort the list.  When I have completed sorting I want to
grab a page of items, say 1,000 of them which I do easily by using
list_data[x:x+1000]

Now I want to add an additional key/value pair to each dictionary in
the list, incrementing them by 1 each time.  So, if I grabbed page 2
of the list I would get:

[{'a':'a', 'b':'b', 'position':1001}, {'c':'c', 'd':'d', 'position':
1002}, ...]

Any way to do that with list comprehension?  Any other good way to do
it besides iterating over the list?

Thanks