Kth Largest Select in Python

select.py

def Select(a, i, first=0, last=None):
    if last is None:
        last = len(a)-1
    p = Pivot(a, first, last)
    if p == i:
        return a[p]
    if p < i:
        return Select(a, i, p+1, last)
    return Select(a, i, first, p-1)

swap_count = 0

def Pivot(a, first, last):
    def Swap(i, j):
        global swap_count
        (a[i], a[j]) = (a[j], a[i])
        swap_count += 1

    i = (first+last)/2
    Swap(first, i)
    v = a[first]
    j = first+1
    for i in range(first+1, last+1):
        if a[i] < v:
            Swap(i, j)
            j += 1
    Swap(first,j-1)
    return j-1

import random

size = 200
a = [random.randrange(size) for i in range(size)]
s = list(a)
s.sort()

for i in range(size):
    t = list(a)
    swap_count = 0
    x = Select(t,i)
    print "%d -> %d (%s) [%d swaps]" % (i, x, "Good" if x == s[i] else "FAIL", swap_count)

print s