[Python-Dev] RE: [Patches] [Patch #102915] xreadlines : readlines :: xrange : range

[Tim Peters]

[Guido]
> I only see a factor of 3 between fastest and slowest, and
> readline is only about 60% slower than readlines_sizehint.

[Neil]
> Could it be that your using the CVS version of Python which
> includes Andrew's cool glibc getline enhancement?

[Guido]
> Bingo!

It's a good thing I haven't yet had time to try any speed tests myself,
since I don't have a glibc-enabled platform so Guido and I may have been
tempted to disagree about numbers in public <wink>.

I checked out the source for glibc's getline.  It's pulling the same trick
Perl uses, copying directly from the stdio buffer when it can, instead of
(like Python, and like almost all vendor fgets implementations) doing
getc-in-a-loop.  The difference is that Perl can't do that without breaking
into the FILE* representation in platform-dependent ways.  It's a shame that
almost all vendors missed that fgets was defined as a primitive by the C
committee precisely so that vendors *could* pull this speed trick under the
covers.  It's also a shame that Perl did it for them <wink>.