def quick_sort(A, compare=None):
    """Perform a quicksort on a list of items, A, by recursively dividing 
       and conquering through partitioning."""
    
    # we need the random class to choose pivot values
    from random import Random
    rand = Random()
    
    # do we need our own comparison function? We'll assume that it is a list
    # if integers. The comparison function needs to return -1 for less-than,
    # 0 for equal, and 1 for greater-than the pivot.
    if compare is None:
        compare = lambda item, pivot: (-1, 0, 1)[item > pivot and 2 or int(item is pivot)]

    def divide(S):
        """Choose a pivot and partition the list into three sublists using that
           pivot. Conquer each sublist recursively."""
        length = len(S)
        
        # no need to divide a list of length 0 or 1
        if length < 2:
            return S
        
        # choose a pivot randomly
        pivot_val = S[rand.randrange(0, length)]
        
        # separate the list into 3 partitions
        less = [i for i in S if compare(i, pivot_val) is -1]
        equal = [i for i in S if compare(i, pivot_val) is 0]
        greater = [i for i in S if compare(i, pivot_val) is 1]
        
        # conquer each section by further dividing them
        return conquer(less, equal, greater)
        
    def conquer(L, E, G):
        """Conquer the three partitions by recursively dividing/conquering them
           and join them into the final result."""
        S = []
        S.extend(divide(L)) # join back the now sorted sublists
        S.extend(divide(E))
        S.extend(divide(G))
        return S
    
    # start the partitioning
    return divide(list(A))

if __name__ == "__main__":
    ls = [5, 8, 3, 1, 2, 99, 14, 7]
    print "Unsorted list:", ls
    print "Sorted list:", quick_sort(ls)

Unsorted list: [5, 8, 3, 1, 2, 99, 14, 7]
Sorted list: [1, 2, 3, 5, 7, 8, 14, 99]