[Python-Dev] accumulator display syntax
Guido van Rossum
guido at python.org
Tue Oct 21 16:46:42 EDT 2003
> Iterator expression?
Better. Or perhaps generator expression? To maintain the link with
generator functions, since the underlying mechanism *will* be mostly
the same. Yes, I like that even better.
BTW, while Alex has shown that a generator function with no free
variables runs quite fast, a generator expression that uses variables
from the surrounding scope will have to use the nested scopes
machinery to access those, unlike a list comprehension; not only does
this run slower, but it also slows down all other uses of that
variable in the surrounding scope (because it becomes a "cell"
throughout the scope).
Someone could time how well
y = 1
sum([x*y for x in R])
fares compared to
y = 1
for x in R: yield y*y
for R in (range(N) for N in (100, 1000, 10000)).
--Guido van Rossum (home page: http://www.python.org/~guido/)
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