QFileDialog goes wrong

class MainWindow(QtWidgets.QMainWindow):

    """Main window in GUI.

    Attributes:

    Methods:
    """

    def __init__(self, app, parent=None):
        """Initializes all childs and layouts for MainWindow"""

        # base class constructor
        super(MainWindow, self).__init__(parent)

        # create child widgets
        menu_bar = MenuBar(app, self)
        self.setMenuBar(menu_bar)

        central_widget = QtWidgets.QWidget(self)
        widgets = [ UrlWidget(self), ButtonBar(self), HistoryWidget(self), OutputWidget(self) ]

        # set central widget layout and add widgets
        set_layout(central_widget, QtWidgets.QVBoxLayout(), widgets)

        # set central_widget as central layout for self and edit window title
        self.setCentralWidget(central_widget)
        self.setWindowTitle("Konbāta")

        path = QtWidgets.QFileDialog.getOpenFileName(self, caption="Select an output folder", directory="home/olivier/")[0]