As Russell Brennan points out, this isn't currently possible with ArcPy. ArcGIS 10.3 adds 9 tools to the Geodatabase Administration toolset, but sadly, this still won't be possible natively through ArcPy or any Geoprocessing Tools with the new release. This is yet another reason retiring the SDE command line tools is premature. The use cases just keep piling up in the forums (sorry, GeoNet) where SDE command line tools work and nothing else is available, but Esri is doing their best David Farragut impersonation with this one. Unfortunately for those customers needing to script advanced geodatabase administration tasks, this isn't Mobile Bay and the mines will go off and cause damage. The sdelayer command should work for what you need, at least for the short while it will be around: sdelayer -o {grant | revoke} -l <table,column> -U <user> -A <SELECT,UPDATE,INSERT,DELETE> [-s <server_name>] [-i {<service> | <port#> | <direct connection>}] [-D <database_name>] -u <DB_user_name> [-p <DB_user_password>] [-I] [-q] Starting with ArcGIS 10.1, Esri decided to stop publishing the reference documentation for the tools online. If you install the tools, the reference documentation is there. Since the tools haven't changed much over the years, I usually just look up information in the ArcGIS 10.0 ArcSDE Administration Command Reference.
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