separate_variations.py

# -*- coding: utf-8 -*-

import time

def separate_variations2(lst):
    n = len(lst)
    assert n >= 2

    for bitpattern in xrange(1, 2 ** (n - 1)):
        x = list()
        y = list()
        pat = bitpattern
        for i in lst:
            if bitpattern & 1 == 1:
                x.append(i)
            else:
                y.append(i)
            bitpattern = bitpattern >> 1
        yield tuple(x), tuple(y)

def separate_variations(lst):
    """
    separate a list into 2 lists
    """
    n = len(lst)
    assert n >= 2
    s = set(lst)
    for i in xrange(1, 2 ** (n - 1)):
        x = {lst[c] for c, b in enumerate(reversed(format(i, 'b'))) if b == '1'}
        y = s - x
        yield tuple(x), tuple(y)

mylst = range(0, 20)
time0 = time.clock()
for x in separate_variations(mylst):
    pass
time1 = time.clock()
for x in separate_variations2(mylst):
    pass
time2 = time.clock()

print time1 - time0
print time2 - time1