get-a-cup-of-coffee slow (fwd)

[Grant Griffin]

Michael Linnemann wrote:
> 
> Am Thu, 09 Aug 2001 18:12:31 -0400 Lulu of the Lotus-Eaters wrote:
> 
> >In expanded form:
> >
> >   def gen_sectors3():
> >       print 'Generating (Version 3)...',
> >       lst = []
> >       for i in xrange(65536):
> >           lst.append(chr(i & 0xFF))
> >       for i in xrange(65536):
> >           lst.append(chr((65535 - i) & 0xFF))
> >       print 'done'
> >       return ''.join(lst)
> 
> >I haven't benched it--or even run it--but this will probably even beat
> >'gen_sectors2()'.
> 
> But I did ;-)
> 
> And here is the result:
> 
>   Version 2: 0.006
>   Version 3: 1.005
>   Version 4: 0.054
> 
> I made a gen_sectors4 because V.2 was surprisingly slow:
> 
>     def gen_sectors4():
>        print 'Generating (Version 4)...',
>        s = []
>        forward = []
>        reverse = []
>        for i in xrange(256):
>            forward += [chr(i)]
>            reverse += [chr(255 - i)]

How about?:

             forward.append(chr(i))
             reverse.append(chr(i))

>        s += forward * 256
>        s += reverse * 256
>        print 'done'
>        return "".join(s)
> 
> This is Python2.0 on a Linux machine, only in case it matters...

Cool!  But that one also seems kindda slow compared to #2.  I wonder if
the lists were built using "append" (appending one element) rather than
"+=" (appending a list _containing_ one element).

there-are-obviously-many-"obvious"-ways-to-do-it-<wink>-ly y'rs,

=g2
-- 
_____________________________________________________________________

Grant R. Griffin                                       g2 at dspguru.com
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