Peter Otten wrote:
[EMAIL PROTECTED] wrote:
is there is a neat way to select items from an iterable based on
predicates stored in another iterable without zipping? I can do
something like this:
import itertools
foo = range(10)
# select even numbers
bar = map(lambda i: i%2, foo)
foobarselected = itertools.ifilterfalse(lambda t: t[0], itertools.izip
(bar,foo))
# for simplicity I want to work with the single item list, not the
zipped one
fooselected = list(t[1] for t in foobarselected)
However, it would be nice to have a function combining the last two
instructions. Something like
itertools.ifilterother(bar, foo) -> yield iterator with items from foo
where bar is true
I think it's a good approach to keep the number of primitives low. I find
the list comprehension combined with izip() quite readable:
[v for f, v in izip(bar, foo) if not f(v)]
Peter
If you want an iterator without requiring making a list, you can simply
use parentheses instead of brackets:
agenerator = (v for f, v in izip(bar, foo) if not f(v))
This is perfectly lazy but not immune to problems when foo or bar is
changed before the generator is fully consumed.
James
--
James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095
http://www.jamesstroud.com
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