# QWidget: Must construct a QApplication before a QPaintDevice

**URL:** <https://www.ruby-forum.com/t/qwidget-must-construct-a-qapplication-before-a-qpaintdevice/244977>\
**Category:** GNU Radio\
**Created:** [July 21, 2016, 11:37pm UTC](https://www.ruby-forum.com/t/qwidget-must-construct-a-qapplication-before-a-qpaintdevice/244977 "2016-07-21T23:37:18Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Sadaf\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@Sadaf\_N](https://www.ruby-forum.com/u/Sadaf_N)\
**Post date:** [July 21, 2016, 11:37pm UTC](https://www.ruby-forum.com/t/qwidget-must-construct-a-qapplication-before-a-qpaintdevice/244977/1 "2016-07-21T23:37:18Z")

</div>

HI, I am new to GNUradio. I have run into a problem when i tried to run  
a gnuradio python file but  
the GUI didn’t start. Below is the output.

Executing: /usr/bin/python2 -u  
/home/champly/gr-ieee802-11/examples/wifi\_loopback.py

linux; GNU C++ version 5.4.0 20160609; Boost\_105800;  
UHD\_003.010.000.git-249-gef57ffcb

QWidget: Must construct a QApplication before a QPaintDevice

> > > Done

* * *

System Info:

champly@champly:~/gr-ieee802-11/examples$ lsb\_release -s -d  
Ubuntu 16.04 LTS

hamply@champly:~/gr-ieee802-11/examples$ uname -a  
Linux champly 4.4.0-31-generic #50-Ubuntu SMP Wed Jul 13 00:07:12 UTC  
2016 x86\_64 x86\_64 x86\_64 GNU/Linux

Thank you,  
Best regard