When I try to resize (thumbnail) an image using PIL, the exif data is lost.

What do I have to do preserve exif data in the thumbnail image? When I searched for the same, got some links but none seem to be working.

from PIL import  Image
import StringIO

file_path = '/home/me/img/a.JPG'
im = Image.open( file_path)
THUMB_SIZES = [(512, 512)]
for thumbnail_size in THUMB_SIZES:
    im.thumbnail( thumbnail_size, Image.ANTIALIAS)
    thumbnail_buf_string = StringIO.StringIO()
    im.save('512_' + "a", "JPEG")

The orginal image has exif data, but image im(512_a.JPEG) doesn't.

import pyexiv2
from PIL import  Image

file_path = '/home/../img/a.JPG'
metadata = pyexiv2.ImageMetadata(file_path)
metadata.read()
thumb = metadata.exif_thumbnail
thumb.set_from_file(file_path)
thumb.write_to_file('512_' + "a")
thumb.erase()
metadata.write()

Now I open the image using (Patch Image Inspector) , I can see the exif data