QMainWindow and child widgets size don't match - qt

Question

Probably a noob question, but I'm still learning PySide. So I'm trying to use QMainWindow which has a QFrame and the QFrame has two labels. I'm using QBoxLayouts on QMainWindow and QFrame. The problem is that when I set the QFrame to something like 200x200 then QMainWindow does not resize, it remains too small to display both labels. Correct me if I'm wrong but shouldn't QMainWindow automatically have the right size when using layouts? Additionaly when I output frame.sizeHint() then it outputs PySide.QtCore.QSize(97, 50) but I would expect it to be 200, 200.
The code below will reproduce the problem:
import sys
from PySide import QtGui
class MainWindow(QtGui.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.initUI()
def initUI(self):
#-------
#CREATE WIDGETS
#-------
frame = QtGui.QFrame()
frame.setStyleSheet("QFrame {background-color: yellow}")
frame.setGeometry(0, 0, 200, 200)
someLabel = QtGui.QLabel("SomeLabel")
someOtherLabel = QtGui.QLabel("SomeOtherLabel")
self.setCentralWidget(frame)
#--------
#CREATE LAYOUT
#--------
frameLayout = QtGui.QVBoxLayout()
frameLayout.addWidget(someLabel)
frameLayout.addWidget(someOtherLabel)
frame.setLayout(frameLayout)
mainLayout = QtGui.QVBoxLayout()
mainLayout.addWidget(frame)
self.setLayout(mainLayout)
self.show()
def main():
app = QtGui.QApplication(sys.argv)
mainWindow = MainWindow()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
This is what happens after code is run:

Answer 1

A QMainWindow already has a top-level layout, so you should never set one yourself. All you need to do is set the central-widget, and then add a layout and widgets to that.
Your example can therefore be fixed like this:
frame.setLayout(frameLayout)
# get rid of these three lines
# mainLayout = QtGui.QVBoxLayout()
# mainLayout.addWidget(frame)
# self.setLayout(mainLayout)
self.show()
It's worth noting that there is possibly a bug/misfeature in PySide regarding this, because in PyQt your original script would print a useful error message:
QWidget::setLayout: Attempting to set QLayout "" on MainWindow "", which already has a layout