import sys
from PyQt4 import QtCore, QtGui
class Class1(QtGui.QMainWindow):
def __init__(self):
super(Class1, self).__init__()
self.func()
A QMainWindow provides a layout already, you can't simply replace that with your own. Either inherit from a plain QWidget, or create a new widget and add the layout and buttons to that.
Your naming is confusing too, QButtonGroup isn't a layout. It doesn't actually provide any visible UI. If you need a UI element that groups buttons, you should look at QGroupBox instead.
Here's a simple variation on what you have above:
def func(self):
layout=QtGui.QHBoxLayout() # layout for the central widget
widget=QtGui.QWidget(self) # central widget
widget.setLayout(layout)
number_group=QtGui.QButtonGroup(widget) # Number group
r0=QtGui.QRadioButton("0")
number_group.addButton(r0)
r1=QtGui.QRadioButton("1")
number_group.addButton(r1)
layout.addWidget(r0)
layout.addWidget(r1)
letter_group=QtGui.QButtonGroup(widget) # Letter group
ra=QtGui.QRadioButton("a")
letter_group.addButton(ra)
rb=QtGui.QRadioButton("b")
letter_group.addButton(rb)
layout.addWidget(ra)
layout.addWidget(rb)
# assign the widget to the main window
self.setCentralWidget(widget)
self.show()