The CLI usage documentation provides the following .python-gitlab.cfg file example:
[global]
...
api_version = 3
[somewhere]
...
api_version = 4
...
However, the api_version option in the [global] section seems having no effect.
with [global] api_version = 3:
user@machine:~$ gitlab -d project list
...
DEBUG:urllib3.connectionpool:https:/<host>:443 "GET /api/v3/projects HTTP/1.1" 200 None
...
with [global] api_version = 4: the result is the same, it uses v3 endpoints
FYI:
user@machine:~$ pip freeze | grep gitlab
python-gitlab==1.2.0