pyqt - tansparent background

[nkint]

hi

this is my first forum i hope is right section

i'm with python 2.6 and pyqt 4.7

qanto to make a window with transparent bacground: inside i want do see buttons and see the desktop over it
i've searched in forum but given solutions don't works.

i've tried those methods, in contructor and in paintEvent() override:

self.setStyleSheet("background-color: rgba(255, 255, 255, 0%);")

self.setStyleSheet("background-color: rgba(255, 255, 255, 0%);")

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and

self.setWindowOpacity(0.3)

self.setWindowOpacity(0.3)

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,

self.setBackgroundRole(QtGui.QPalette.Base)		
self.setAttribute(Qt.Qt.WA_NoSystemBackground, True)

self.setBackgroundRole(QtGui.QPalette.Base)		
self.setAttribute(Qt.Qt.WA_NoSystemBackground, True)

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with also

self.setAttribute(Qt.Qt.WA_TranslucentBackground)

self.setAttribute(Qt.Qt.WA_TranslucentBackground)

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the only result i've got is a window with noise inside. if window is small i get noise with color similar to background, if i enlarge it, only black

thanks for your attention

[nkint]

no one got solutions?
also c++ examples are right, but i didn't find anythong on the net that is working in my situations..
and i don't think why i get noise and random pixels