python Quicksort demo

__author__ = 'student'

'''
quicksort
step 1, choose one pivot, such as pivot=la[0]
step 2, scan the data from right side, find data less than pivot, then swap this with pivot
pivot=1  [4] 5 7 3 20 9 [j]
then scan from left side, find data greater than pivot, then swap the position j and i
4 [] 7 3 20 9 5
when i>=j then finish one loop. then put the pivot in the i;
 all data are dived by pivot now. left is less than pivot and right are greater than pivot.
think step by step then do it and try something
step 3. then you have two parts to sort, left part and right part.
recursive  call this method to sort
'''
import random

def quicksort(la,l,r):
    if l>=r :
        return
    left=l;right=r
    pivot=la[left]
    while left < right:
        while left<right and la[right]>pivot:
            right-=1
        if left<right :
            la[left]=la[right]
            left+=1
        while left<right and la[left]<pivot:
            left+=1
        if left<right:
            la[right]=la[left]
    la[left]=pivot
    quicksort(la,l,left-1)
    quicksort(la,left+1,r)

def quicksort2(la):
    if len(la)<=1:
        return la
    return quicksort2([lt for lt in la[1:] if lt<la[0]])+ la[0:1]+quicksort2([ge for ge in la[1:] if ge>=la[0]])

import sys
sys.setrecursionlimit(999)

la=[]
def generatenumbers(la,len):
    for x in range(len):
        la.extend([random.randint(1,50)])
generatenumbers(la,1000)
print la
quicksort(la,0,len(la)-1)
print la