pythonsys

`sys.dont_write_bytecode` not working if I just import the function instead of the whole sys library

I'm trying to delete the __pycache__ folder for importing modules and if I:

from sys import dont_write_bytecode 
dont_write_bytecode = True 

import folder.modulename as modulename

the folder still gets created, but if I import all the library as shown below:

import sys 
sys.dont_write_bytecode = True 

import folder.modulename as modulename

the folder it's not created.

Can someone explain why this happens and if it's possible to avoid importing the whole sys library?

Solution

  • Yes. When you write from sys import dont_write_bytecode, that creates a new name in your namespace and binds it to the same object as the one in sys. When you write dont_write_bytecode = True, you are binding a different boolean object to your name, replacing your old binding. It has absolutely no effect on the dont_write_bytecode variable that is part of sys.

    However, to correct another misconception, using from sys import xxx is NOT any more efficient than import sys.

    The import you have written is exactly equivalent to:

    import sys
dont_write_bytecode = sys.dont_write_bytecode
del sys

    The from sys import construct always has to import the entire module.