smarnach

import timeit
import numpy
import scipy.ndimage.morphology

def f0(a, kernel):
    b = numpy.convolve(a, kernel, mode="same") > 1
    b[1:] |= b[:-1]
    b[:-1] |= b[1:]
    return b

smarnach

class MyRECache(dict):
    def __missing__(self, regex):
        return self.setdefault(regex, re.compile(regex))

smarnach

In [1]: import numpy

In [2]: a = numpy.random.randint(100, size=100)

In [3]: ((25 < a) & (a < 100)).sum()
Out[3]: 72

smarnach

>>> class A(object):
...     i = 3
...     a = [i for x in range(3)]
... 
>>> class A(object):
...     i = 3
...     a = list(i for x in range(3))
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>

smarnach

In [1]: a = array.array("i", range(100000))

In [2]: b = array.array("i", range(100000))

In [3]: %timeit for i, x in enumerate(a): b[i] = 2 * x
10 loops, best of 3: 20.6 ms per loop

In [4]: a = range(100000)

In [5]: b = range(100000)

smarnach

import random
import timeit

def inter_reduce(sets):
    return reduce(set.intersection, sets)

def inter_for(sets):
    sets = iter(sets)
    result = next(sets)
    for s in sets:

smarnach

def f(list_of_lists):
    sets = {}
    for lst in list_of_lists:
        s = set(lst)
        for x in set(lst):
            if x in sets:
                t = sets[x]
                for y in t:
                    sets[y] = s

smarnach

In [3]: consume = collections.deque(maxlen=0).extend

In [4]: def f(a):
   ...:     consume(x for x in a)
   ...:     

In [5]: def g(a):
   ...:     consume(a)
   ...:     

smarnach

Tmimings on a Linux box, 32-bit kernel, 32-bit userland

Python version:                                        2.7                    3.1
-s"a=10**20;n=3" "(a>>n)&1"                   0.224 usec per loop     0.161 usec per loop
-s"a=10**20;n=3" "not not(a & (1 << n))"      0.155 usec per loop     0.183 usec per loop
-s"a=10**200;n=3" "(a>>n)&1"                  0.39 usec per loop      0.303 usec per loop
-s"a=10**200;n=3" "not not(a & (1 << n))"     0.158 usec per loop     0.177 usec per loop
-s"a=10**10;n=3" "(a>>n)&1"                   0.223 usec per loop     0.153 usec per loop
-s"a=10**10;n=3" "not not(a & (1 << n))"      0.158 usec per loop     0.18 usec per loop
-s"a=10**9;n=3" "(a>>n)&1"                    0.0734 usec per loop    0.152 usec per loop

smarnach

#include <unistd.h>
#include <stdio.h>

int main(int argc, const char **argv)
{
    char c[10240] = {0};
    int fd;

    sscanf(argv[1] + 8, "%i", &fd);    // skip "/dev/fd/"
    read(fd, c, 10239);