qgis.core import to Python 3

Question

I had a pure Python 3 configured for myself and recently installed QGIS (just QGIS, not OSGeo4W). I need to keep my initial Python 3 but also add qgis.core module. Can it be done with no harm to my previously installed Python? I saw that installing OSGeo4W should help but anyway there is some paths need to set in the user environment settings.