Short quicksort in python

quicksort.py

import random; import operator; from six.moves import range, reduce
def swap(arr, iv, ip, dir):
    if iv == ip + dir: arr[iv], arr[ip] = arr[ip], arr[iv]
    else: arr[iv], arr[ip + dir], arr[ip] = arr[ip + dir], arr[ip], arr[iv]
shift = lambda (cmp, dir, arr, ip), iv: (cmp, dir, arr, ip) if cmp(arr[iv], arr[ip]) else (swap(arr, iv, ip, dir) or (cmp, dir, arr, ip + dir))
def qs(arr, bgn=0, end=None):
    if end is None: end = len(arr) - 1 - bgn
    if end - bgn < 1: return arr
    ip = bgn if end - bgn == 1 else random.randint(bgn + 1, end - 1)
    _, _, _, ipl = reduce(shift, range(ip - 1, bgn - 1, -1), (operator.le, -1, arr, ip))
    _, _, _, ipr = reduce(shift, range(ip + 1, end + 1, +1), (operator.ge, +1, arr, ipl))
    return qs(arr, bgn, ipr) and qs(arr, ipr+1, end)