Question

What does the interpreter do in these cases?

1. from xyz import Abc
2. from xyz import *

Does it has to parse the full file xyz.py anyway? Should one way be faster then the other? Or is it merely a matter of readability that people prefer the first approach to the second?

Answer 1

It should not make any difference performance-wise, because the entire module has to be processed either way.

The difference is one of readability, and pollution of namespaces. To minimize the chances of name-clashes, and unexpected behavior due to name-hiding, it is prudent to only import those objects that you are actually using.

from Martijn Pieters:

All top-level names you import into a module, can also be imported again from that module
unless a __all__ parameter has been set. Thus you usually end up with far more items being
added to your local namespace than you bargained for