PyQt. How to translate function value to lineEdit? Please, help to find a better approach

Question

I want to create a simple programm (in QtDesigner) that executes a function when button is clicked, and displays the value of this function in a LineEdit. And here is my code:

class MyForma1(object):
    def AddWidgets1(self, Form):
        Form.setObjectName(_fromUtf8("Form"))
        Form.resize(613, 545)
        self.pushButton = QtGui.QPushButton(Form)
        self.pushButton.setGeometry(QtCore.QRect(244, 352, 111, 51))
        self.pushButton.setObjectName(_fromUtf8("pushButton"))
        self.lineEdit = QtGui.QLineEdit(Form)
        self.lineEdit.setGeometry(QtCore.QRect(242, 290, 111, 20))
        self.lineEdit.setObjectName(_fromUtf8("lineEdit"))
        self.retranslateUi(Form)

        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("clicked()")), Form.changeText)

    def retranslateUi(self, Form):
        self.pushButton.setText(_translate("Form", "Click me", None))
        self.lineEdit.setText(_translate("Form", "functionvalue", None))

class MyForma2(QtGui.QDialog, MyForma1):
    def __init__(self, z11=0):
        QtGui.QDialog.__init__(self)
        self.AddWidgets1(self)
        self.z = z11

    def myfunc1(self):
        self.z+=1

    def changeText(self):
        self.myfunc1()
        self.lineEdit.setText(str(self.z))

if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    Forma = MyForma2()
    Forma.show()
    sys.exit(app.exec_())

Actually, it works fine, but i dont like the way it is done, i want to make it more exquisite. The problem here, is that the button "executes" a function and value translation together. And i think it would be better if the button executes only a function and additionaly there is something that constantly translates the value of this function to LineEdit separately from the button. For example, there could be a situation when the function value, which needs to be constantly monitored, could be affected not only by the button, but also by some other events (ex: incoming signal from COM-port). And in this case, it would be great to emmit a signal every time the function is changed, not only when button is pressed.

Answer 1

Checkout this example:

#!/usr/bin/env python
#-*- coding:utf-8 -*-

#---------
# IMPORT
#---------
from PyQt4 import QtGui, QtCore

#---------
# MAIN
#---------
class MyWindow(QtGui.QWidget):
    valueChanged  = QtCore.pyqtSignal(int)

    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)

        self.value = 0

        self.pushButtonAdd = QtGui.QPushButton(self)
        self.pushButtonAdd.setText("Add!")
        self.pushButtonAdd.clicked.connect(self.on_pushButtonAdd_clicked)

        self.pushButtonSubtract = QtGui.QPushButton(self)
        self.pushButtonSubtract.setText("Subtract!")
        self.pushButtonSubtract.clicked.connect(self.on_pushButtonSubtract_clicked)

        self.lineEditValue = QtGui.QLineEdit(self)
        self.lineEditValue.setText(str(self.value))

        self.layoutVertical = QtGui.QVBoxLayout(self)
        self.layoutVertical.addWidget(self.pushButtonAdd)
        self.layoutVertical.addWidget(self.pushButtonSubtract)
        self.layoutVertical.addWidget(self.lineEditValue)

    @QtCore.pyqtSlot()
    def on_pushButtonAdd_clicked(self):
        self.valueChanged.emit(1)

    @QtCore.pyqtSlot()
    def on_pushButtonSubtract_clicked(self):
        self.valueChanged.emit(-1)

    def setValue(self, value):
        self.value += value
        self.lineEditValue.setText(str(self.value))

if __name__ == "__main__":
    import sys

    app = QtGui.QApplication(sys.argv)
    app.setApplicationName('MyWindow')

    main = MyWindow()
    main.resize(333, 111)
    main.valueChanged.connect(main.setValue)
    main.show()

    sys.exit(app.exec_())

In this example, to change the value manually you can call main.setValue(34)