trying to set values iteratively in numpy

gistfile1.py

import os
import sys
import arcpy
import numpy
import math
from arcpy.sa import *
arcpy.CheckOutExtension('Spatial')
arcpy.env.overwriteOutput = True

cwd = os.getcwd()
srcPath = cwd + "\\src-img\\"
srcImgs = os.listdir(srcPath)

for img in srcImgs:
	path = srcPath + img
	arr = arcpy.RasterToNumPyArray(path)
	i = 2000
	while i < 2100:
		j = 2000
		while j < 2100:
			arr[i][j] = 5
			++j
		++i
		
	print 'break point'