Quicksort implementations for the blog

quicksort.py

def quicksort(xs):
    def sort(xs, l, r):
        if (l == r):
            return
        
        i, j = l, r
        pivot = xs[(i + j) / 2]
        
        while (i <= j):
            while (xs[i] < pivot):
                i += 1
            while (pivot < xs[j]):
                j -= 1
            
            if (i <= j):
                xs[i], xs[j] = xs[j], xs[i]
                
                i += 1
                j -= 1
    
    i, j = 0, len(xs) - 1
    sort(xs, i, j)