List comprehension - NameError: name '_[1]' is not defined ?

[mario ruggier]

The listcomps exploration above was primarily an attempt
(unsuccessful) to make this piece of code go a little faster:

s = " text %(item)s text "
acc = []
for value in iterator:
    some_dict["item"] = value
    acc.append(s % evaluator)
"".join(acc)

The item=value pair is essentially a loop variable, and the evaluator
(something like the gie instance above) uses it via the updated
some_dict.

Is there any way to express the above as a list comp or so? Any ideas
how it might be made to go faster?

m.