[FIXED] PySide \ PyQt: How to return value to UI after button click?

Issue

I am trying to return a path from a browse folder dialog box.

I have tried passing the instance object or even attribute to the call and setting it there:

self.browseBtn.clicked.connect(myExporter.browseFolder(self))

or

self.browseBtn.clicked.connect(myExporter.browseFolder(self.path))

But this doesn't work. It causes the browser dialog to pop open immediately upon load and then once you choose a folder it errors out with : Failed to connect signal clicked().

I have tried to set the clicked call to a return, with no luck:

result = self.browseBtn.clicked.connect(myExporter.browseFolder)

Can someone lead me in the right direction as far as how to return a value, when you are dealing with separate classes handling the UI and logic? Also... is it bad practice to be separating them like this? I know I could probably easily solve this if I threw everything into just one python file, but I figured that is not proper.

Here is my ui file (ui.py):

from PySide import QtCore, QtGui

class Ui_Dialog(object):
    def __init__(self):
        self.path =""

    def setupUi(self, Dialog, myExporter):
        Dialog.setObjectName("Dialog")
        Dialog.resize(382, 589)
        ...
        .......
        ............. 
        .................
        self.retranslateUi(Dialog)
        self.tabWidget.setCurrentIndex(1)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

        self.browseBtn.clicked.connect(myExporter.browseFolder)

Here is my exporter file (exporter.py):

class Exporter(object):
    def __init__(self):
        ...
        ......

    def browseFolder(self):
        ...
        .......
        do something
        ...........    
        return path

Here is my load/test file (loadExporter.py):

import ui as interface
import exporter as exporter
from PySide import QtCore, QtGui

app = QtGui.QApplication.instance()
if app is None:
    app = QtGui.QApplication(sys.argv)       
Dialog = QtGui.QDialog()
myExporter = exporter.Exporter()
myUI = interface.Ui_Dialog()
myUI.setupUi(Dialog, myExporter)
Dialog.show()
app.exec_()

Solution

It's not necessarily bad to have them in separate files. Having a separate file for certain widgets is a good thing especially if those widgets can be reused.

I would have my main file have a QMainWindow class.

class MyWindow(QtGui.QMainWindow):
    pass

if __name__ == "__main__":
    QtGui.QApplication([])

    mywindow = MyWindow()
    mywindow.show()

    sys.exit(QtGui.qApp.exec_())

Wrapping the app functionality in if __name__ == "__main__" prevents this code from being run when another file tries to import this file.

A signal (self.browserBtn.clicked) calls a callback method. Everything is an object in python.

def my_func():
    pass

new_func_name = my_func # my_func can be reassigned like any variable

my_func is an object. self.browseBtn.clicked.connect(my_func) passes my_func as a variable to be called later.

When self.browserBtn.clicked.emit() happens (on user click) it is the same as calling the connected functions my_func(). Other signals may pass values to callback functions self.lineEdit.textChanged.connect(my_func) calls 'my_func(new_text)'

You want your function to call everything for you.

def open_file(filename=None):
    """Open a file."""
    # If a filename isn't given ask the user for a file
    if filename is None:
        filename, ext = QtGUi.QFileDialog.getOpenFileName(None, "Open File", ".../My Documents/")
        # You may have to use the ext to make a proper filename

    # Open the file
    with open(filename, "r") as file:
        file.read()

self.browserBtn.clicked.connect(open_file)

Structure

...
import mywidget

class MyWindow(QtGui.QMainWindow):
    def __init__(self):
        super().__init__()
        ...
        self.show_file = QtGui.QLineEdit()
        self.setCentralWidget(self.show_file)

        self.exporter = mywidget.Exporter()
        self.browserBtn.clicked.connect(self.open_file)

    def open_file(self, filename=None):
        """Open a file."""
        path = self.exporter.browseFolder()
        # Do something with the path
        self.show_file.setText(path)

if __name__ == "__main__":
    QtGui.QApplication([])

    mywindow = MyWindow()
    mywindow.show()

    sys.exit(QtGui.qApp.exec_())

Answered By - justengel