PyQt4 doesn't execute eventFilter()

[akiross]

Hello there,
I'm working with PyQt and trying to filter an event, but it doesn't seem to work. I wrote a simple test (which seems correct to me), but doesn't work too.

Here the code:

#!/usr/bin/python
 
import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *
 
class SomeFilter(QObject):
	def eventFilter(self, obj, ev):
		print("Event filtering ok")
		return False
 
class MainWidget(QMainWindow):
	def __init__(self):
		QMainWindow.__init__(self)
		self.installEventFilter(SomeFilter())
 
app = QApplication(sys.argv)
w = MainWidget()
w.show()
sys.exit(app.exec_())

#!/usr/bin/python

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

class SomeFilter(QObject):
	def eventFilter(self, obj, ev):
		print("Event filtering ok")
		return False

class MainWidget(QMainWindow):
	def __init__(self):
		QMainWindow.__init__(self)
		self.installEventFilter(SomeFilter())

app = QApplication(sys.argv)
w = MainWidget()
w.show()
sys.exit(app.exec_())

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The print is never executed (on loading, resizing, repainting and closing)

Am I doing this wrong?
Thanks