PyQt4 filename dialog

Question

I am a bit of a novice so be kind ;-)

I had a GUI that I made using PyQt4 and python 2.6 with a working file dialog, (ie you clicked a button and a window popped up and allowed you to pick a file to load/save). The code for the GUI is like 2000 lines, so i will include the bits i think are important:

from PyQt4 import QtGui as qt
from PyQt4 import QtCore as qc

class NuclearMotion(qt.QWidget):
    def __init__(self, parent=None):
        super(NuclearMotion, self).__init__(parent)

        file_button = qt.QPushButton("Use data from file")
        mainLayout = qt.QGridLayout()
        mainLayout.addWidget(file_button, 14, 8, 1, 2)

    def choose_file():
        file_name = qt.QFileDialog.getOpenFileName(self, "Open Data File", "", "CSV data files (*.csv)")

        self.connect(file_button, qc.SIGNAL("clicked()"), choose_file)
        self.setLayout(mainLayout)

    if __name__ == '__main__':
        import sys
        app = qt.QApplication(sys.argv)
        NuclearMotionWidget = NuclearMotion()
        NuclearMotionWidget.show()
        sys.exit(app.exec_())

The above works absolutely fine. I typed all the code for it manually using various tutorials. I have now made a new GUI using QT designer and pyuic4 to convert it to a .py file. Now I can't make the file dialog work. The below code results in a Type error:

from PyQt4 import QtCore, QtGui

class Ui_mainLayout(object):
    def setupUi(self, mainLayout):
        mainLayout.setObjectName(_fromUtf8("mainLayout"))
        mainLayout.resize(598, 335)
        mainLayout.setTabPosition(QtGui.QTabWidget.North)
        mainLayout.setTabShape(QtGui.QTabWidget.Rounded)
        mainLayout.setElideMode(QtCore.Qt.ElideLeft)

        self.basic_tab = QtGui.QWidget()
        self.file_button = QtGui.QPushButton(self.basic_tab)
        QtCore.QObject.connect(self.file_button, QtCore.SIGNAL("clicked()"), self.choose_file)

    def choose_file(self):
        file_name = QtGui.QFileDialog.getOpenFileName(self, "Open Data File", "", "CSV data files (*.csv)")

if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    mainLayout = QtGui.QTabWidget()
    ui = Ui_mainLayout()
    ui.setupUi(mainLayout)
    mainLayout.show()
    sys.exit(app.exec_())

This code produces the GUI just fine and everything else works ok including signals. Any idea what I am doing wrong!?

Answer 1

Your class should inherit (directly or indirectly) from QtCore.QObject to be able to handle signals. The first one inherits from QWidget, which does the job.