How To Have Qt Run Asynchroneously For Interactive Use Like Matplotlib's Ion Mode?

I want to be able to launch a Qt interface from the python interpreter, with the command line returning immediately, so that I can continue using python while being able to use the

Solution 1:

It is not necessary to use a thread or the complement of another library, you just have to execute the commands but you should not call the exec_() method of QApplication since it uses the python interactive console eventloop.

$ python
Python 3.8.2 (default, Feb 26 2020, 22:21:03) 
[GCC 9.2.1 20200130] on linux
Type "help", "copyright", "credits" or "license" for more information
>>>from PyQt5.QtWidgets import QApplication, QGraphicsRectItem, QGraphicsScene, QGraphicsView, QMainWindow>>>classRect(QGraphicsRectItem):...defmousePressEvent(self, event):...print("foo")...>>>app = QApplication([])>>>window = QMainWindow()>>>window.setGeometry(100, 100, 400, 400)>>>view = QGraphicsView()>>>scene = QGraphicsScene()>>>rect = Rect(0, 0, 150, 150)>>>scene.addItem(rect)>>>view.setScene(scene)>>>window.setCentralWidget(view)>>>window.show()

IPython

As the IPython docs points out, %gui backend must be used to enable the GUI event loops. In the case of PyQt5/PySide2, %gui qt5 must be used at the beginning.

$ ipython
Python 3.8.2 (default, Feb 262020, 22:21:03) 
Type'copyright', 'credits'or'license'for more information
IPython 7.13.0 -- An enhanced Interactive Python. Type'?'forhelp.

In [1]: %gui qt5                                                                                                                                                                                

In [2]: from PyQt5.QtWidgets import QApplication, QGraphicsRectItem, QGraphicsScene, QGraphicsView, QMainWindow                                                                                 

In [3]: classRect(QGraphicsRectItem): 
   ...:   defmousePressEvent(self, event): 
   ...:     print("foo") 
   ...:                                                                                                                                                                                         

In [4]: app = QApplication([])                                                                                                                                                                  

In [5]: window = QMainWindow()                                                                                                                                                                  

In [6]: window.setGeometry(100, 100, 400, 400)                                                                                                                                                  

In [7]: view = QGraphicsView()                                                                                                                                                                  

In [8]: scene = QGraphicsScene()                                                                                                                                                                

In [9]: rect = Rect(0, 0, 150, 150)                                                                                                                                                             

In [10]: scene.addItem(rect)                                                                                                                                                                    

In [11]: view.setScene(scene)                                                                                                                                                                   

In [12]: window.setCentralWidget(view)                                                                                                                                                          

In [13]: window.show()