[Python-Dev] Stupid Python Tricks, Volume 38 Number 1

2001年1月20日 16:13:41 -0500

[Tim]
> huge.join('""')

[Guido]
> Points off for obscurity though!

The Subject line was "Stupid Python Tricks" for a reason <wink>. Those who
don't know the language inside-out should be tickled by figuring out why it
even *works* (hint for the baffled: you have to view '""' as a sequence
rather than as an atomic string).
> My favorite for this is:
>> '"%s"' % huge
>> Worth a microbenchmark?

Absolutely! I get:
 obvious 15.574
 obscure 8.165
 sprintf 8.133
after running:
ITERS = 1000
indices = [0] * ITERS
def obvious(huge):
 for i in indices: '"' + huge + '"'
def obscure(huge):
 for i in indices: huge.join('""')
def sprintf(huge):
 for i in indices: '"%s"' % huge
def runtimes(huge):
 from time import clock
 for f in obvious, obscure, sprintf:
 start = clock()
 f(huge)
 finish = clock()
 print "%12s %7.3f" % (f.__name__, finish - start)
runtimes("x" * 1000000)
under current 2.1a1. Not a dead-quiet machine, but the difference is too
small to care. Speed up huge.join attr lookup, and it would probably be
faster <wink>. Hmm: if I boost ITERS high enough and cut back the size of
huge, "obscure" eventually becomes *slower* than "obvious", and even if the
"huge.join" lookup is floated out of the loop. I guess that points to the
relative burden of calling a bound method. So, in real life, the huge.join
approach may well be the slowest!
>> not-entirely-sure-i'm-channeling-on-this-one-ly y'rs - tim

> Give up the channeling for a while -- there's too much interference in
> the air from the Microsoft threaded stdio debate still. :-)

What debate? You need two arguably valid points of view for a debate to
even start <wink>.
gloating-in-victory-vicious-in-defeat-but-simply-unbearable-in-
 ambiguity-ly y'rs - tim