python function x takes exactly n arguments (n-1 given)

Question

I am writing a program which is supposed to give me data of a chart when I click certain buttons. I have given the program as far as I am right now. (I still have to connect the last 4 buttons but the first one works.) Now there is another problem: I used to have a chart displayed as I clicked on "One Plot" but since I activated "First Button", the chart does not appear anymore due to the problem mentioned problem. This is the script:

class Main(QMainWindow, Ui_MainWindow):

    def __init__(self, parent=None):
        super(Main, self).__init__(parent)
        self.setupUi(self)
        self.fig_dict = {}
        self.mplfigs.itemClicked.connect(self.changefig)

        self.button1.setText("First Point")
        self.button1.clicked.connect(self.onClickButton1)

        self.dialogbutton1 = PopUp(self)

        fig = Figure()
        self.addmpl(fig)


    @QtCore.pyqtSlot()
    def changefig(self, item):
        text = item.text()
        self.rmmpl()
        self.addmpl(self.fig_dict[str(text)])


    def addfig(self, name, fig):
        self.fig_dict[name] = fig
        self.mplfigs.addItem(name)


    def addmpl(self, fig):
        self.canvas = FigureCanvas(fig)
        self.mplvl.addWidget(self.canvas)
        self.canvas.draw()
        self.toolbar = NavigationToolbar(self.canvas, self.mplwindow, coordinates=True)
        self.mplvl.addWidget(self.toolbar)


    def onClickButton1(self):
        # When button 1 is clicked, I do the following
        print "does nothing now."
        self.dialogbutton1.exec_()


    def rmmpl(self,):
        self.mplvl.removeWidget(self.canvas)
        self.canvas.close()
        self.mplvl.removeWidget(self.toolbar)
        self.toolbar.close()


class PopUp(QtGui.QDialog):

    def __init__(self, parent=None):
        super(PopUp, self).__init__(parent)
        self.buttonBox = QtGui.QDialogButtonBox(self)
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtGui.QDialogButtonBox.Cancel|QtGui.QDialogButtonBox.Ok)
        self.textBrowser = QtGui.QTextBrowser(self)
        self.textBrowser.append("x - Coordinate = 0 y - Coordinate = 0.031451")
        self.verticalLayout = QtGui.QVBoxLayout(self)
        self.verticalLayout.addWidget(self.textBrowser)
        self.verticalLayout.addWidget(self.buttonBox)


if __name__ == '__main__':
    import sys
    from PyQt4 import QtGui
    import numpy as np

    fig1 = Figure()
    ax1f1 = fig1.add_subplot(111)
    ax1f1.plot(np.random.rand(5))

    app = QtGui.QApplication(sys.argv)
    main = Main()
    main.addfig('One plot', fig1)

    print main.fig_dict
    main.show()
    sys.exit(app.exec_())

Answer 1

In class Main , you are calling changefig function as self.mplfigs.itemClicked.connect(self.changefig) .

But function definition of changefig is def changefig(self, item): which expects two arguments - self and item .

When you called changefig - self.mplfigs.itemClicked.connect(self.changefig) , only self is passed. But item is not passed.

That's why you are getting that error.

It should be self.mplfigs.itemClicked.connect(self.changefig(item))