I haven't found a solution to this for python...if you have access to the computer running Tableau Server, it looks like you are able to clear the cache using a tabadmin or redis command (see link for more). tabadmin requires server outages...not sure if the redis route would.
I'm still testing out the image endpoint, so I've worked around image caching by duplicating the views on tableau server and pinging the server for the duplicate views...not sure if your application is more mature.
I read that the vizportal cache is not the same one as the server cache. Not sure if that's true.
Since I need the cached image soon after updating the source. Would changing vizportal.rest_api.view_image.max_age to 5 minutes be loading the image too frequently? I'm worried about slowing down the server
Is there any update yet? On Tableau Server (Windows, 10.5), setting the above mentioned parameter to 0 or 1 doesn't seem to have an effect, as the image generated via the Rest API endpoint does not reflect any changes in the live data connection (while the Dashboard web view is updated), thus it still seems to be cached.
Is there any option or response parameter to check the status/date of the image cache?