urllib

>>> from urllib import parse
>>> post_url = "https://www.baidi.com/post"
>>> path = "/n/123"
>>> url = parse.urljoin(post_url,path)
>>> url
'https://www.baidi.com/n/123'
>>> path = "https://www.baidi.com/n/123"
>>> url = parse.urljoin(post_url,path)
>>> url
'https://www.baidi.com/n/123'

from urllib import parse
post_url = "https://www.baidi.com/post"
path = "/n/123"
url = parse.urljoin(post_url,path)

urllib parse的urljoin()可以根据目标url有无域名而自动添加