kth smallest number.py

import random
def kthSmallest(arr, l, r, k):
    if (k > 0 and k <= r - l + 1):
        pos = randomPartition(arr, l, r)
        if (pos - l == k - 1):
            return arr[pos]
        if (pos - l > k - 1):
            return kthSmallest(arr, l, pos - 1, k)
        return kthSmallest(arr, pos + 1, r,k - pos + l - 1)
    return 999999999999
def swap(arr, a, b):
    temp = arr[a]
    arr[a] = arr[b]
    arr[b] = temp
def partition(arr, l, r):
    x = arr[r]
    i = l
    for j in range(l, r):
        if (arr[j] <= x):
            swap(arr, i, j)
            i += 1
    swap(arr, i, r)
    return i
def randomPartition(arr, l, r):
    n = r - l + 1
    pivot = int(random.random() * n)
    swap(arr, l + pivot, r)
    return partition(arr, l, r)
if __name__ == '__main__':
    arr = [12, 3, 5, 7, 4, 19, 26]
    n = len(arr)
    k = 3
    print("K'th smallest element is",kthSmallest(arr, 0, n - 1, k))