[PyQt] PyQt application frozen if run in localhost; OK if SSH'd to another host

Arrieta superjuanelo at gmail.com
Thu Jun 23 17:26:52 BST 2011

Consider the following PyQT application (helloworld.py):

import sys
from PyQt4 import QtGui

def main():
    app = QtGui.QApplication(sys.argv)
    win = QtGui.QPushButton("Hello, World!")
    return app.exec_()

if __name__ == "__main__":

If I run ($python helloworld.py) this application from a shell in my
computer, I see the main container for the button, but the button itself
never renders. After a few clicks on the [x] of the main container, I
receive a warning window stating:

Window with title "helloworld.py" is not responding. This window belongs to
application helloworld.py (PID=2000, hostname=localhost). Do you wish to
terminate this application? (All unsaved data in this application will be
lost.) [Yes] [No]

If I then use the same shell window to SSH to another machine in our network
and run the exact same program (we have an NFS file system; I see the same
files in every machine) it runs as expected. In fact, even if I SSH back to
my original computer I can run the application.

This happens with all the PyQt applications I have developed for my group,
and it happens on every computer in our network: the applications won't run
locally, but run perfectly fine if the user is connected to the terminal via
SSH (let me insist, even if SSH'd to your local, physical computer!)

Do you have any suggestion for debugging/tracking down this problem?

Many thanks.

Python 2.6.5
Qt 4.6.2
Red Hat Linux Enterprise Edition (4)

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