xreadlines (was Re: while true: !!!)

[Jeff Epler]

On Thu, 14 Dec 2000 11:14:38 +0100, Alex Martelli
 <aleaxit at yahoo.com> wrote:
>...if it was able to iterate over already-opened file-like objects, rather
>than having to open actual files itself, it WOULD conceptually solve it
>all.  I wonder how hard it would be to generalize fileinput in this way --
>probably not very (the in-place-rewriting option would be incompatible
>with having already-opened file-like objects in the list, of course).

xreadlines takes a file object, not a filename, as its argument.

>If [using readline] was a performance problem, it could of course
>also be fixed in a future fileinput version without changing code that
>uses it (again, in-place-rewriting would probably have to inhibit the
>optimization, although that isn't entirely clear).

xreadlines internally uses fp.readlines(sizehint), so 
	for line in xreadlines.xreadlines(fp): pass
is just about as fast as
	for line in fp.readlines(): pass
except that it will not require storage for the whole file.

Jeff