[HOW TO] Set preferred binding from code before import

[melMass]

I'm pretty sure I already relied on that in the past but I cannot find anything in the readme about it.

I'm using Qt.py as a dependency in a library that might be used in both PyQt5 and PySide2.
I want to do something like this:

__qt__bindings__ = ["PyQt5","PySide2"]

import Qt
...

[MHendricks]

It's an environment variable. QT_PREFERRED_BINDING

import os
# Use os.path.pathsep for linux/windows compatibility. Linux uses `:` and windows uses `;`
os.environ['QT_PREFERRED_BINDING'] = os.path.pathsep.join(["PyQt5","PySide2"])

import Qt
import my_library.Qt
# Both Qt modules use the same binding
assert Qt.__binding__ == 'PyQt5'
assert my_library.Qt.__binding__ == 'PyQt5'

However if you are wanting to control this for your library and not cause problems if other libraries don't work well with PyQt5 you should use the newer environment variable so that only your Qt.py module attempts to use PyQt5. In this example you have a copy of Qt.py inside my_library.

import os
os.environ['QT_PREFERRED_BINDING_JSON'] = "{"my_library.Qt":["PyQt5","PySide2"]}"

import Qt
import my_library.Qt
# Only my_library.Qt uses the PyQt5 binding, other Qt modules work as normal
assert Qt.__binding__ == 'PySide2'
assert my_library.Qt.__binding__ == 'PyQt5'

I would recommend setting these variables globally for the session, not inside your library. I set QT_PREFERRED_BINDING_JSON as part of a plugin for Maya and startup scripts for 3ds Max, Nuke, etc.

[melMass]

Thanks a lot for the detailed answer!
I mainly wanted to do this for testing and to limit the library to PyQt5 & PySide2 Only