python hashlib.sha1 发生 UnicodeEncodeError

被这个错搞了半天，尝试一堆encode,decode，还尝试了
import sys
reload(sys)
sys.setdefaultencoding('utf8')
也不管用。
最后查到需要转成utf-8，再调用sha1.

hashlib.sha1(s).hexdigest()
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-81: 
ordinal not in range(128)

Apparently hashlib.sha1 isn't expecting a unicode object, but rather a sequence of bytes in a strobject. Encoding your unicode string to a sequence of bytes (using, say, the UTF-8 encoding) should fix it:

>>> import hashlib
>>> s = u'é'
>>> hashlib.sha1(s.encode('utf-8'))