Em Ter, 2006-02-14 às 20:14 -0800, Farel escreveu:
> Which is Faster in Python and Why?
>
> jc = {}; m = []
> x = [ [1,2,3,4,5,6,7,8,9],[..],.......] # upwards of 10000 entries
> def binm()
> for item in x:
> b = item[:]; b.sort(); bc = 0
> for bitem in b: bc += int(bitem)
> try: m = jc[bc]
> except: m = []
> if not b in m:
> m.append(b); jc[bc]=m
Why do you copy the list and sort it if you're just summing its
elements? Instead of
b = item[:]; b.sort(); bc = 0
for bitem in b: bc += int(bitem)
you can do just
bc = sum(int(i) for i in item)
or, if the order *really* matters, what is very strange, you can do
bc = sum(int(i) for i in sorted(item))
Another thing, if you want to have in the values of the dictionary jc
only unique elements, you can use sets:
>>> a = set()
>>> print a
set([])
>>> a.add(10)
>>> print a
set([10])
>>> a.add(10)
>>> print a
set([10])
>>> a.add(10)
>>> print a
set([10])
So, the final example would be (assuming that you don't need to sum in
order):
def binm():
for item in x:
bc = sum(int(i) for i in item)
try:
jc[bc].add(b)
except KeyError:
jc[bc] = set([b])
Looks prettier, have less statements and is (or should be) faster. This
only works in Python 2.4, but you can adapt it to run on other versions,
too.
Cheers,
Felipe.
--
"Quem excele em empregar a força militar subjulga os exércitos dos
outros povos sem travar batalha, toma cidades fortificadas dos outros
povos sem as atacar e destrói os estados dos outros povos sem lutas
prolongadas. Deve lutar sob o Céu com o propósito primordial da
'preservação'. Desse modo suas armas não se embotarão, e os ganhos
poderão ser preservados. Essa é a estratégia para planejar ofensivas."
-- Sun Tzu, em "A arte da guerra"
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