As has been already described in this thread, the official list of all included standard library modules is available programmatically as sys.stdlib_module_names in the Python interpreter you’re targeting, which internally lives in Python/stdlib_module_names.h. Additionally, all formally documented top-level modules are listed in the the module index of the docs. As far as standard library modules are concerned, could you explain how this is insufficient for your use case?
As for third party packages on PyPI, by definition they are third party and thus not supported directly by the Python core team. You can get the full list of all PyPI packages by various methods, e.g. the Simple HTTP API, the old JSON API, the new JSON API, the BigQuery dataset, etc. See the API docs for more details and e.g. this previous thread for specifics.