The import method of not importing everything has some postive impacts, though probably small.

- reduce startup time
- reduces code size as your code no longer has to refer to the base class. ie qtcore.qrectangle becomes just qrectangle
- not sure if references become a bit faster internally, but feels right to me.

I would also use constants where possible rather than have them values recalculated, as is often the case in code.

given most heavy lifting code is done inside the libraries like qt I,m not sure python is much slower, and if you ae not using libraries why not especially given the richness of them. of course YMMV