I think what you want is this. Calling version on raw will give you HTTP version. (I found the example of server running HTTP 1.0 using Shodan for testing purposes)
>>> import requests
>>> response = requests.get("http://104.71.136.252/", timeout=60, verify=False)
>>> response.raw.version
10
>>> response = requests.get("http://stackoverflow.com", timeout=60, verify=False)
>>> response.raw.version
11
This is not mentioned in the docs directly, I found it by using PyCharm's autocomplete feature. But I have looked into it. The reason why is HTTP version returned as integer is historical.
Requests for python3 uses urllib3. Urllib3's class urllib3.response.HTTPResponse is backwards compatible with httplib’s HTTPResponse see urllib3 docs
Now if it's backwards compatible you have to check documentation for httplib and if you search you'll find
HTTP protocol version used by server. 10 for HTTP/1.0, 11 for HTTP/1.1.
Here is the exact link HTTPResponse.version