[Python-Dev] List comprehensions

[Paul Prescod]

"M.-A. Lemburg" wrote:
> 
> If it means writing code in square brackets: yes --
> I don't see any real benefit other than confusing the reader...
> it doesn't even gain any performance 

We've discussed making them lazy, which would improve performance in
some cases...especially with infinite lists. :)

> Oh, so I won't get these with list comprehension ? Hmm, then
> I'm posting on the wrong thread, I guess ;-)

Well, I didn't want to say it, but...

> Say, wouldn't it make more sense to
> have these notations generate tuples (which are immutable and
> could thus be stored as constants) rather than lists ?!

I think that the notation should create a generator.

> The for-loop opcode could even make some use of this by not generating
> a tuple at all (it could use a special mutable counter like the
> one available in my speedup patch for 1.5:

We discussed this yesterday. Anyhow, you don't need to use tuples to get
the speedup. You just have to recognize the pattern in a peephole
optimizer.
-- 
 Paul Prescod - Not encumbered by corporate consensus
Simplicity does not precede complexity, but follows it. 
	- http://www.cs.yale.edu/~perlis-alan/quotes.html