Recursive rename in python script

#!/usr/bin/env python
import fnmatch
import os

root = os.getcwd()
pattern = "*.JPG"

for root, dirs, files in os.walk(root):
    for filename in fnmatch.filter(files, pattern):
        #print (os.path.join(root, filename))
        full_src = os.path.join(root, filename)
        full_dst = full_src.replace('.JPG','.jpg')
        os.rename(full_src, full_dst)
        print "Renaming {0} to {1}".format(full_src, full_dst)