def random_combination(iterable, nquartets):
    """
    Random selection from itertools.combinations(iterable, r). 
    Use this if not sampling all possible quartets.
    """
    pool = tuple(iterable)
    size = len(pool)
    indices = random.sample(xrange(size), nquartets)
    return tuple(pool[i] for i in indices)
def random_combination(iterable, nquartets):
    """
    Random selection from itertools.combinations(iterable, r). 
    Use this if not sampling all possible quartets.
    """
    pool = tuple(iterable)
    size = len(pool)
    indices = random.sample(xrange(size), nquartets)
    return tuple(pool[i] for i in indices)
def random_combination ( iterable , nquartets ) : pool = tuple ( iterable ) size = len ( pool ) indices = random . sample ( xrange ( size ) , nquartets ) return tuple ( pool [ i ] for i in indices )
Random selection from itertools.combinations(iterable, r). 
    Use this if not sampling all possible quartets.
Random selection from itertools . combinations ( iterable r ) . Use this if not sampling all possible quartets .