# OCC.Display.backend module

`get_loaded_backend`()

`get_qt_modules`()
  tuple : ( QtCore, QtGui, QtWidgets, QtOpenGL )
    here QtWidgets shadows QtGui when a PyQt4 or PySide module is loaded this is the most coherent way to get PyQt5 compliant code
  ValueError
    when no Qt backend has been yet loaded informs the user to call load_backend or that no Qt python module ( PyQt5, PyQt4 or PySide ) is found

`load_backend`(backend_str=None)

  loads a gui backend

  If no Qt (such as PyQt5, PyQt4 or PySide) backend is found, wx is loaded

  The search order for pythonocc compatible gui modules is:
    PyQt5, PyQt4, PySide, Wx

  Wx is imported when no Qt backend is found.

  backend_str : str

  > specifies which backend to load

  > backend_str is one of ( “qt-pyqt5”, “qt-pyqt4”, “qt-pyside”, “wx” )

  > if no value has been set, load the first module in gui module search order

  str
    the name of the loaded backend one of ( “qt-pyqt5”, “qt-pyqt4”, “qt-pyside”, “wx” )
  ValueError
    - when a backend is already loaded
    - when an invalid backend_str is specified
  ImportError
    when the backend specified in `backend_str` could not be imported

`load_pyqt4`()

  returns True is PyQt4 found, else False

`load_pyqt5`()

  returns True is PyQt5 found, else False

`load_pyside`()

  returns True is PySide found, else False

`load_wx`()

  returns True is wxPython found, else False

`loaded_backend`()