Use the Universal Encoding Detector:
>>> import chardet
>>> chardet.detect(urlread("http://google.cn/"))
{'encoding': 'GB2312', 'confidence': 0.99}
The other option would be to just use wget:
import os
h = os.popen('wget -q -O foo1.txt http://foo.html')
h.close()
s = open('foo1.txt').read()