QtCore.QObject.connect in a loop only affects the last instance

I have got a loop. I created a QCheckBox and put it in a QTableWidget cell, and everything is Ok. In each step of loop I have called a connect function, for myslot SLOT, but only the last QCheckBox instance is applied. I googled a lot and have found many people have my problem. I have applied their solutions, but my problem remains.

for row in xrange(len(uniqueFields)):
    instance = QtGui.QCheckBox(uniqueFields[row], findInstance.tableWidget)
    print QtCore.QObject.connect(instance,
        QtCore.SIGNAL(_fromUtf8("stateChanged (int)")),
        lambda: findInstance.projectsInstance.myslot(
                    "TWCH", findInstance, instance.text(),
                    instance.checkState(), instance))
    findInstance.tableWidget.setRowCount(findInstance.tableWidget.rowCount() + 1)
    findInstance.tableWidget.setCellWidget(row, 0, instance)

Note: my connect function return True.

How to create connect function in a loop that enumerates all of the instances?

Solution 1:

Put the loop variable in a default argument, like this:

lambda state, instance=instance: findInstance.projectsInstance.myslot(
    "TWCH", findInstance, instance.text(), instance.checkState(), instance)

This will give each lambda its own local copy of the instance variable.

EDIT

Here's a simple script that demonstrates how to use default lambda arguments:

from PyQt4 import QtGui

class Window(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        layout = QtGui.QVBoxLayout(self)
        for index in range(4):
            instance = QtGui.QCheckBox('Checkbox(%d)' % index, self)
            instance.stateChanged.connect(
                lambda state, instance=instance:
                    self.mySlot(instance.text()))
            layout.addWidget(instance)

    def mySlot(self, text):
        print('clicked: %s' % text)


if __name__ == '__main__':

    import sys
    app = QtGui.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

Solution 2:

I have same problem , you should use functools.partial such as:

for key, val in a_DICT_THAT_YOU_STORED_YOUR_OBJECTS_AND_STRINGS:
    obj = partial(   findInstance.projectsInstance.myslot,arg1="TWCH",arg2=self,arg3=key,arg4=val.checkState() )
    QtCore.QObject.connect(val, QtCore.SIGNAL(_fromUtf8("stateChanged (int)")), obj)

Of course, argX should set to your real name of your argument of your function name.