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Newsgroups: comp.lang.python
Date: Mon, 23 Jan 2012 10:56:49 -0800 (PST)
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Subject: Re: Looking under Python's hood: Will we find a high performance or clunky engine?
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:19275

=E5=9C=A8 2012=E5=B9=B41=E6=9C=8823=E6=97=A5=E6=98=9F=E6=9C=9F=E4=B8=80UTC+=
8=E4=B8=8A=E5=8D=882=E6=97=B601=E5=88=8611=E7=A7=92=EF=BC=8CRobert Kern=E5=
=86=99=E9=81=93=EF=BC=9A
> On 1/22/12 3:50 PM, Rick Johnson wrote:
> >
> > What does Python do when presented with this code?
> >
> > py>  [line.strip('\n') for line in f.readlines()]
> >
> > If Python reads all the file lines first and THEN iterates AGAIN to do
> > the strip; we are driving a Fred flintstone mobile. If however Python
> > strips each line of the lines passed into readlines in one fell swoop,
> > we made the correct choice.
> >
> > Which is it Pythonistas? Which is it?
>=20
> The .readlines() method is an old API that predates the introduction of=
=20
> iterators to Python. The modern way to do this in one iteration is to use=
 the=20
> file object as an iterator:
>=20
>    [line.strip('\n') for line in f]

This is more powerful by turning an object to be iterable.

But the list comprehension violates the basic operating=20
principle of the iteratee chaining rule in programming.
=20
I know manny python programmers just abandon the list comprehension
in non-trivial processes.=20