CPython itself doesn't have guaranteed way to do this kind of thing.  There is no tracking of which types clear memory let alone which API calls may make copies of data in places within their C that are not explicitly cleared afterwards.  We do not have a plan to implement this.

For data that MUST NOT remain in memory in any form anywhere as soon as code is done with it, the best thing to do is isolate all code inputting, processing, and clearing that within the confines of a lower level extension module or a short lived subprocess.