Robert Kern wrote:
Mike Meyer wrote:
Ok, we've added list comprehensions to the language, and seen that they were good. We've added generator expressions to the language, and seen that they were good as well.
I'm left a bit confused, though - when would I use a list comp instead of a generator expression if I'm going to require 2.4 anyway?
If you want a list right away you'd use a list comprehension. X =[i for i in something() if somethingelse()] random.shuffle(X) print x[23]
On the other hand it's generator expressions which should be used only when the code can be written in as a pipe. For example a filter of a -otherwise- very long list:
make_fractal_with_seed (x for x in range(100000000) if fibonacci_prime (x))
Never. If you really need a list
list(x*x for x in xrange(10))
Sadly, we can't remove list comprehensions until 3.0.
Why??? Then we should also remove: x=[] to x=list() x=[1,2,3] to x=list(1,2,3)
I think "list" is useful only: 1) to subclass it 2) to convert a list/tuple/string to a list, which is done extremely fast.
But for iterators I find the list comprehension syntax nicer.
jfj
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