TypeError: POST data should be bytes or an iterable of bytes. It cannot be of type str.

[alatriste-lee]

response = urlopen("https://openapi.baidu.com/oauth/2.0/token", data=urlencode(data))

[makelove]

response = urlopen("https://openapi.baidu.com/oauth/2.0/token", data=urlencode(data).encode('utf-8'))

你肯定是在用python3
改为urlencode(data).encode('utf-8')
就行了。