this code sends data in a different way if using python 2.6 or python 2.7

>>> import urllib2
>>> url = 'http://server.com/post_image?tid=zoV6LJ'
>>> f = open('test.jpg')
>>> data = f.read()
>>> res = urllib2.urlopen(url, data)

I checked it with wireshark and the data is sent in a different way when using python 2.7

The code works for python2.5 and python2.6