Python progress of single file copy progressbar

#!/usr/bin/env python
import os

SOURCE_FILENAME="/tmp/2.png"
TARGET_FILENAME="/tmp/3.png"

source_size = os.stat(SOURCE_FILENAME).st_size
copied = 0
source = open(SOURCE_FILENAME, 'rb')
target = open(TARGET_FILENAME, 'wb')

while True:
    chunk = source.read(32768)
    if not chunk:
        break
    target.write(chunk)
    copied += len(chunk)
    print '\r%02d%%' % (copied * 100 / source_size),

source.close()
target.close()