import functools

mysum = functools.partial(functools.reduce, lambda x, y: x+y)
mysum([1,2,3,2,1])

mymax = functools.partial(functools.reduce, lambda x, y: x if x>=y else y)
mymax([1,2,3,2,1])

myaverage = lambda list_ : mysum(list_) / len(list_)
myaverage([1,2,3])