pyqt signal not emitted in QAbstractTableModel

Question

So i'm writing an application and using QTableView with QAbstractTableModel to display my data. In each row a checkbox is placed in the first column and when it is checked or unchecked, i want a pyqtsignal CheckBoxValue be emitted to MyTable . But it seems that the connected function self.checkboxchecked in MyTable is not called. Although I used to use pyqtSignal several times without any issue, i'm stuck here and couldn't solve it out.

Thank you all for spending time taking care of my question!

import operator  # used for sorting
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4 import QtGui, QtCore

class MyTable(QWidget):
    Checkboxcheckvalue = pyqtSignal(bool)
    Rowselected = pyqtSignal(int)
    doubleClicked = pyqtSignal(int)
    def __init__(self,  *args):
        QWidget.__init__(self, *args)
        # setGeometry(x_pos, y_pos, width, height)
        # self.setGeometry(70, 150, 1326, 582)
        self.dataList = []
        self.header = []
        self.currentrow = []
        self.setWindowTitle("Click on the header to sort table")

        self.table_model = MyTableModel(self, self.dataList, self.header)
        self.table_view = QTableView()
        #self.table_view.setSelectionMode(QAbstractItemView.SingleSelection)
        self.table_view.setSelectionMode(QtGui.QAbstractItemView.SingleSelection)
        self.table_view.setSelectionBehavior(QtGui.QAbstractItemView.SelectRows)
        # bind cell click to a method reference
        self.table_view.clicked.connect(self.showSelection)
        self.table_view.clicked.connect(self.selectRow)

        self.table_view.doubleClicked.connect(self.doubleclickedaction)

        self.table_model.CheckBoxValue.connect(self.checkboxchecked)




        self.table_view.setModel(self.table_model)
        # enable sorting
        self.table_view.setSortingEnabled(True)

        layout = QVBoxLayout(self)
        layout.addWidget(self.table_view)
        self.setLayout(layout)



    def update_model(self):
        self.table_model = MyTableModel(self, self.dataList, self.header)
        self.table_view.setModel(self.table_model)
        self.table_view.update()

    def findLabelName(self,rowindex):
        return self.dataList[rowindex][-1]

    def doubleclickedaction(self,index):
        self.doubleClicked.emit(index.row())
        self.currentrow = index.row()
        print ('doubleclicked',self.findLabelName(index.row()))


    def checkboxchecked(self,value):
        print ('table checkboxchecked',self.currentrow,value)
        # self.currentrow = index.row()
        if value == True:
            self.Checkboxcheckvalue.emit(True)
        else:
            self.Checkboxcheckvalue.emit(False)


    def selectedLabel(self,index):
        return self.findLabelName(index.row())



    def showSelection(self, item):
        cellContent = item.data()
        # print(cellContent)  # test
        sf = "You clicked on {}".format(cellContent)
        # display in title bar for convenience
        self.setWindowTitle(sf)

    def selectRow(self, index):
        self.Rowselected.emit(index.row())
        self.currentrow = index.row()
        print("current row is %d", index.row())
        pass


class MyTableModel(QAbstractTableModel):
    """
    keep the method names
    they are an integral part of the model
    """

    CheckBoxValue = pyqtSignal(bool)
    def __init__(self, parent, mylist, header, *args):
        QAbstractTableModel.__init__(self, parent, *args)
        self.mylist = mylist
        self.header = header

    def setDataList(self, mylist):
        self.mylist = mylist
        self.layoutAboutToBeChanged.emit()
        self.dataChanged.emit(self.createIndex(0, 0), self.createIndex(self.rowCount(0), self.columnCount(0)))
        self.layoutChanged.emit()

    def rowCount(self, parent):
        if self.mylist != []:
            return len(self.mylist)
        else:
            return 0

    def columnCount(self, parent):
        if self.mylist != []:
            return len(self.mylist[0])-1
        else:
            return 0

    def data(self, index, role):
        if not index.isValid():
            return None
        if (index.column() == 0):
            value = self.mylist[index.row()][index.column()].text()
        else:
            value = self.mylist[index.row()][index.column()]
        if role == QtCore.Qt.EditRole:
            return value
        elif role == QtCore.Qt.DisplayRole:
            return value
        elif role == QtCore.Qt.CheckStateRole:
            if index.column() == 0:
                if self.mylist[index.row()][index.column()].isChecked():
                    return QtCore.Qt.Checked
                else:
                    return QtCore.Qt.Unchecked

    def headerData(self, col, orientation, role):
        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
            return self.header[col]
        return None

    def sort(self, col, order):
        """sort table by given column number col"""
        if col != 0:
            pass
        else:
            col = -1
        self.emit(SIGNAL("layoutAboutToBeChanged()"))
        self.mylist = sorted(self.mylist, key=operator.itemgetter(col))
        if order == Qt.DescendingOrder:
            self.mylist.reverse()
        self.emit(SIGNAL("layoutChanged()"))
        print 'sorted'

    def flags(self, index):
        if not index.isValid():
            return None
        if index.column() == 0:
            return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsUserCheckable
        else:
            return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable

    def setData(self, index, value, role):
        if not index.isValid():
            return False
        if role == QtCore.Qt.CheckStateRole and index.column() == 0:
            if value == QtCore.Qt.Checked:
                self.mylist[index.row()][index.column()].setChecked(True)
                print('checked',index.row())
                self.CheckBoxValue.emit(True)

            else:
                self.mylist[index.row()][index.column()].setChecked(False)
                print('unchecked',index.row())
                self.CheckBoxValue.emit(False)
        self.dataChanged.emit(index, index)
        return True

if __name__ == '__main__':
    app = QApplication([])
    header = ['name', 'type', 'segment', 'exit', 'entry']
    dataList = [
        [QtGui.QCheckBox('line9'), 'line', '058176', '01', '1705','line9'],
        [QtGui.QCheckBox('line3'), 'line', '058176', '02', '1705','line3'],
        [QtGui.QCheckBox('line6'), 'line', '058176', '03', '1705','line6'],
        [QtGui.QCheckBox('line1'), 'line', '058176', '04', '1705','line'],
        [QtGui.QCheckBox('line4'), 'line', '058176', '01', '1705','line4'],
        [QtGui.QCheckBox('area4'), 'area', '058176', '02', '1705','area4'],
        [QtGui.QCheckBox('area2'), 'area', '058176', '02', '1705','area2'],
        [QtGui.QCheckBox('area8'), 'area', '058176', '01', '1705','area8'],
    ]

    win = MyTable()
    win.dataList = dataList
    win.header = header
    win.update_model()
    win.show()
    app.exec_()

Answer 1

In your case you have created a table_model in the MyTable constructor, and with that object you have made the connection, but later in the update_model method you have created a new model so the previous model has been deleted and its connections as well.

def update_model(self):
    self.table_model = MyTableModel(self, self.dataList, self.header)
    self.table_view.setModel(self.table_model)
    self.table_model.CheckBoxValue.connect(self.checkboxchecked)
    self.table_view.update()

Although I prefer to update the model, instead of creating a new model for it, I would create a method to update the data:

class MyTableModel(QAbstractTableModel):
    """
    keep the method names
    they are an integral part of the model
    """

    CheckBoxValue = pyqtSignal(bool)
    def __init__(self, parent, mylist, header, *args):
        QAbstractTableModel.__init__(self, parent, *args)
        self.mylist = mylist
        self.header = header

    def update_model(self,  mylist, header):
        self.beginResetModel()
        self.mylist = mylist
        self.header = header
        self.endResetModel()

    [...]

and in the update_model of the Table:

class MyTable(QWidget):
    [...]
    def update_model(self):
        self.table_model.update_model(self.dataList, self.header)