如评论中所述，github使用发布数据进行身份验证，因此您应该在

As mentioned in the comments, github uses post data for authentication so you should have your creds in the data parameter.
The elements you have to submit are 'login', 'password', and 'authenticity_token'. The value of 'authenticity_token' is dynamic, but you can scrape it from '/login'.
Finally submit data to /session and you should have an authenticated session.

s = requests.Session()
r = s.get('https://www.github.com/login')
tree = html.fromstring(r.content)
data = {i.get('name'):i.get('value') for i in tree.cssselect('input')}
data['login'] = username
data['password'] = password
r = s.post('https://github.com/session', data=data)