Question

Thanks in advance for taking the time to read this. Apologies that it is somewhat verbose. But hopefully it fully explains the problem. Stripped code demonstrating the issue is included.

I’m having an issue with PyQt4 SIGNAL/SLOTS. While I can make everything work fine if I am writing in a single file, I can’t make things work if I some of the functions I wish to use are moved to sub-directories/classes.

I’ve looked through the Python Bindings document I can see how this works when using a single file. But what I am trying to do is this:

• main.py file in root dir which contains the MainWindow __init__ code.
• This file imports a number of widgets. Each widget is stored in its own sub-directory. All sub-directories contain an __init__.py file. These sub-directories are inside of a directory called ‘bin’, which is itself in the root dir
• Some of these widgets need to have SIGNAL/SLOT links between them This is where I fall down.

So the file structure is:

 - main.py
 - bin/textEditor/__init__.py
 - bin/textEditor/plugin.py
 - bin/logWindow/__init__.py
 - bin/logWindow/plugin.py

The following code shows the problem. This code creates a very basic main window that contains a central QTextEdit() widget and a dockable QTextEdit() widget. All that happens is that when the text in the central widget is changed, the same text is shown in the dockable widget. The example works. But it does so by connecting the signal textChanged() in the bin/textEditor/plugin.py file that creates the central QTextEdit() with a function in main.py. I would like it to do exactly the same thing but connexted to the updateUi function in bin/textEditor/plugin.py

If anyone could shed some light on this, I would be hugely grateful. I’m sure it is simple. But direction to any tutorials that cover this or statements that I am doing it all very wrong are equally appreciated!. Thanks again for your time:

### main.py
import os
import sys
# Import PyQT modules
from PyQt4.QtCore import *
from PyQt4.QtGui import *

# Start the main class
class MainWindow(QMainWindow):

    # Initialise
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)

        # Name and size the main window
        self.setWindowTitle("EDITOR/LOG")
        self.resize(800, 600)

        import bin.logWindow.plugin as logWindow
        logWindow.create(self)

        import bin.textEditor.plugin as textEditor
        textEditor.create(self)

    def updateUi(self): 
        # I can connect to this function from within bin/textEditor/plugin.py (see 
        # below) but I want to connect to the function located in 
        # bin/textEditor/plugin.py instead
        text = self.editor.toPlainText()
        self.logWidget.setText(text)

# Run the app
def main():
    app = QApplication(sys.argv)
    form = MainWindow()
    form.show()
    app.exec_()
# Call main
main()

The code inside of the two plugin files is:

### bin/textEditor/plugin.py
# Import PyQT modules
from PyQt4.QtCore import *
from PyQt4.QtGui import *

def create(self):
    # Add a dockable widget
    self.logDockWidget = QDockWidget("Log", self)
    self.logDockWidget.setObjectName("LogDockWidget")
    self.logDockWidget.setAllowedAreas(Qt.LeftDockWidgetArea|
                                       Qt.RightDockWidgetArea)

    self.logWidget = QTextEdit()
    self.logDockWidget.setWidget(self.logWidget)
    self.addDockWidget(Qt.LeftDockWidgetArea, self.logDockWidget)

And

### bin/logWindow/plugin.py
Import PyQT modules
from PyQt4.QtCore import *
from PyQt4.QtGui import *

def create(self):

    # Create a text editing box
    self.editor = QTextEdit()

    # Add to main window
    self.setCentralWidget(self.editor)

    # connect text change to update log window. This is presumably what I need to 
    # change so that it connects to the function below instead of the on in main.py
    self.connect(self.editor, SIGNAL("textChanged()"), self.updateUi)

def updateUi(self):
    text = self.editor.toPlainText()
    self.logWidget.setText(text)

Answer 1

For starters, is there a reason you’re using a very old version of the PyQt release document? The new one is: here

There are a few things you are doing that are a bit unusual. Generally import statements in python are placed at the top of the file (to more easily see dependencies), but I assume you’re doing this to support a more generalized import system for plugins in the future.

It seems like the basic problem is you’re trying to connect a signal source to a slot in another object, without storing that other object in a particular place. To do this you probably need to either make the connection in main, make a neutral “updateUi” slot that emits it’s own special signal that all the plugins are waiting for, or just keep a reference to those subobjects in main and be careful with the initialization order.