I understand that you want offline access to Sheets using Python. If I understood the situation correctly, you only need to give an eye to this guide about OAuth 2.0 for Desktop Apps, especially the part about calling Google APIs. Please, ask me any doubts about this approach.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…