Python wrapper for C++ STL?

[Alex Martelli]

"Andrew Dalke" <dalke at acm.org> wrote in message
news:90s9s1$5oj$1 at slb6.atl.mindspring.net...
>
> Rainer Deyke wrote
> >I tend to use a dictionary where all values are None for sets.
>
> For a bit more performance, use a number, like 0 or 1.
> Using None requires a name lookup.

Nice point!  Copying None to a local variable (when you
know you'll need it a zillion times in a loop) may
ameliorate some of this, and the ability to check with
'is' rather than with '==' may give a tiny advantage:

-- finti.py:

def acheck_oneis(r):
    for c in r:
            if c is 1: return

import time
r = range(2,1000000)

for fun in (acheck_noneeq, acheck_noneis,
            acheck_noneleq, acheck_nonelis,
            acheck_oneeq, acheck_noneis):
    t1=time.time();fun(r);t2=time.time()
    print fun.func_name, t2-t1

-- end of finti.py

D:\PySym>python finti.py
acheck_noneeq 2.41399991512
acheck_noneis 2.05300009251
acheck_noneleq 2.01300001144
acheck_nonelis 1.73199999332
acheck_oneeq 1.75299990177
acheck_noneis 2.0830000639

D:\PySym>python finti.py
acheck_noneeq 2.41399991512
acheck_noneis 2.03299999237
acheck_noneleq 1.98200011253
acheck_nonelis 1.68299996853
acheck_oneeq 1.72200000286
acheck_noneis 2.04299998283

D:\PySym>

I'm not sure why 'is' should be measurably
faster for None and myNone, while being a
bit slower for 1 -- maybe it's crucially
dependent on the values one is testing.  But,
at least on my machine, using a local variable
set to None, and testing with 'is', seems to
be a WEE bit faster than the second-best way,
using 1 and testing with '=='.


Alex