functools.reduce( cmp, it, 2*(it[0],) ) if it else None

import functools
import random
from time import time

def minmax1(iterable):
    minm = None
    maxm = None
    for item in iterable:
       if maxm is None or item > maxm:
          maxm = item
       if minm is None or item < minm:
          minm = item
    return minm, maxm

def minmax( it, key = lambda self: self ):
    return functools.reduce( lambda pair, x: (x,x) if pair is None else ( +min(x, pair[0], key=key), max(x, pair[1], key=key) ), it, None )

def minmax2(iterable):
    return min(iterable), max(iterable)

def minmax3(iterable):
    isorted = sorted(iterable)
    return isorted[0], isorted[-1]

def minmax4(it):
    def cmp( pair, x ):
        if x < pair[0]: return x, pair[1]
        if x > pair[1]: return pair[0], x
        return pair
    return functools.reduce( cmp, it, 2*(it[0],) ) if it else None

data = range(2000000)
random.shuffle(data)
for fun in minmax, minmax1, minmax2, minmax3, minmax4:
    start = time()
    print("result for {0}: {1}, 'time spent:{2}".format( fun.__name__, fun(data), time() - start ))

def minmax5(iterable):
    itera = iter(iterable)
    minm = maxm = itera.next()
    for item in itera:
        if item > maxm:
            maxm = item
        elif item < minm:
            minm = item
    return minm, maxm