I think there is a higher probability of answer on the dedicated mailng list, so I take the freedom to transfer the message (originally posted on the sematic web mailing list)

---------- Forwarded message ---------
From: Jean-Claude Moissinac <jean-claude.moissinac@telecom-paristech.fr>
Date: lun. 7 janv. 2019 à 11:04
Subject: Querying Wikidata
To: semantic-web <semantic-web@w3.org>


Hello,

Is there a good mean to query the sparql wdqs service of wikidata?
I've tried some python code to do it, with relative success.
Success, because some requests gives the expected result.
Relative, because the same query sometimes gives an empty response either from my code or directly in the WDQS interface, where it's possible to see that a sparql query sometimes gives an empty response, sometimes the expected reponse without message or status to know that the response is erroneous.
(demo is difficult, because it seems to depend of the load of the wdqs service)
I've found the following info:
* https://www.mediawiki.org/wiki/Wikidata_Query_Service/User_Manual#Query_limits, which suggest a possible error HTTP code 429, which I never receive
* https://phabricator.wikimedia.org/T179879, which suggest a possible connexion with OAuth, but such possibility is never documented in the official documentation
 
None of them gives a practical method to get a response and trust it.

Have you some advices?


--
Jean-Claude Moissinac