PyQt4 Give Focus to Widget as it is called by the MainWindow and set as CentralWidget?

Question

I want to give Focus to a QLineEdit as soon as it appears... in other cases (all Widgets within the same class) it was possible with .setFocus() - but here this doesn't work. My candidates are .activateWindow()and .raise_(), but I couldn't figure it out how to use them.

edit: My goal is to be able to type into the QLineEdit directly from the keyboard without the need to hit the tab key or click with the mouse in advance.

Here an example of the relevant parts in question (functional):

import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *

class Quiz(QWidget):
    def __init__(self):
        QWidget.__init__(self)

        edit = QLineEdit("Select & Focus")
        edit.selectAll()
        edit.setFocus()             # doesn't work - no effect at all

        vbox = QVBoxLayout()
        vbox.addWidget(edit)
        self.setLayout(vbox)


class MainWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)

        startQuiz = QAction("Start Quiz", self)
        startQuiz.triggered.connect(self.startQuizQuestions)

        menubar = self.menuBar()
        quizMenu = menubar.addMenu("&Quiz")
        quizMenu.addAction(startQuiz)

        self.setGeometry(300, 300, 500, 400)
        self.setWindowTitle("xyz")
        self.show()

    def startQuizQuestions(self):
        newQuiz = Quiz()
        self.setCentralWidget(newQuiz)


def main():
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

If you're seeing me terribly misusing Python or PyQt4... feel free to criticise, I want to learn.

edit: I found in the PySide Docs for .activateWindow this discouraging "comment": "On Windows, if you are calling this when the application is not currently the active one then it will not make it the active window." - But I mean it IS the active Window (=MainWindow) it is just an other Widget in the CentralWidget of the active Window. (?)

Answer 1

It works if you give the widget a parent.

Here is the init function of the widget with a new parent argument, used for the QWidget. Then the QWidget is used as parent for the label.

def __init__(self, parent=None):
    QWidget.__init__(self, parent)

    edit = QLineEdit("Select & Focus", self)
    edit.selectAll()
    edit.setFocus()             # works now

    vbox = QVBoxLayout()
    vbox.addWidget(edit)
    self.setLayout(vbox)

After that you have to pass the MainWindow as parent to the widget like this:

newQuiz = Quiz(self)