Refusing to import PyQt5 because PyQt4.QtCore is already imported.

[Soren Christensen]

Hi,

 I wanted to give vispy a try and build SIP and PyQt from source.

I can import PyQt5 without errors.

If I try to use Vispy, it refuses to use PyQt5 as backend, apparently because PyQt4.QtCore is already loaded.  How can I prevent the Qt4 module from getting loaded?

(See below for 2 line example)

Thanks!

Soren

>>> import vispy

>>> vispy.use(app="PyQt5")

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "/home/sorenc/.local/lib/python2.7/site-packages/vispy/util/wrappers.py", line 95, in use

    vispy.app.use_app(app)

  File "/home/sorenc/.local/lib/python2.7/site-packages/vispy/app/_default_app.py", line 47, in use_app

    default_app = Application(backend_name)

  File "/home/sorenc/.local/lib/python2.7/site-packages/vispy/app/application.py", line 49, in __init__

    self._use(backend_name)

  File "/home/sorenc/.local/lib/python2.7/site-packages/vispy/app/application.py", line 218, in _use

    raise RuntimeError(msg)

RuntimeError: Could not import backend "PyQt5":

Refusing to import PyQt5 because PyQt4.QtCore is already imported.

[Soren Christensen]

0 views in 2 days!

What did I do wrong?

[Soren Christensen]

It turns out the problem comes from launching the code from spyder.  Apparently the Qt4 module is somehow detected as loaded when I run it this way. If I run from cmd line it works.

I still don't have a solution for using spyder in case anyone has any ideas.

Thanks!

[Luke Campagnola]

You did nothing wrong, Soren. We're just busy people  ;)

The problem is that when you run your script from Spyder, it imports several packages into the running process (presumably for debugging purposes), one of which is PyQt4. I am not even sure if it is possible to use both Qt5 and Qt4 in the same process. Perhaps there is a way to get spyder to launch your code without modifying it, though..

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[Soren Christensen]

Thanks!
That is helpful. I will return with an update once I get a chance to investigate.

Soren

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[Soren Christensen]

For others with this problem: Turns out it was spyder doing a default import that include qt4 - see here for how to disable/change the path:

http://stackoverflow.com/questions/14400993/spyder-default-module-import-list

in short:Tools > Preferences > Console > Advanced Settings > PYTHONSTARTUP replacement

[Luke Campagnola]

Thanks Soren!

[Traveler Hauptman]

Thanks soren!