Command line and GUI tools : need a single threading solution

Adrian Casey news at
Tue Jan 11 04:09:26 EST 2005

Phil Thompson wrote:

>> I have a collection of multi-threaded command line tools which I want
>> wrap a
>> PyQt gui around.  I'm using queues to route messages from the command
>> line tools to the PyQt gui. The command line tools use python threads to
>> do
>> their work.  The gui uses a QThread object to read incoming messages.
>> This does not work consistently - and I've since read that mixing python
>> threads and QThreads is a bad idea.  The command line tools work well
>> using
>> python threads.
> How well mixing the two threading APIs works depends on version numbers. A
> PyQt generated with SIP v4.x (rather than SIP v3.x) with Python v2.4
> should be Ok.
>> I don't want to maintain two copies of the tools - one for command line
>> and
>> another for the PyQt version.
>> I'm thinking it may be possible to modify the command line tools to use
>> qt
>> threads instead of native python threads.  Is this the way to go?  Are
>> there other options?
> Using QThreads only should work - just tell the QApplication ctor that you
> have a console application.
> Phil

I'm running python 2.4, sip-4.0 and PyQt-x11-gpl-3.11 (or .13 - not sure as
I'm not at work).

A little more detail.

My script, if invoked from the command line, creates a queue object (let's
call it logQueue) which is used to take the output from each individual
thread.  If invoked via the gui, the script is passed a logQueue created by
the gui.  Each thread dumps its output using logQueue.put().  There are
other queues which are used to service threaded access to a database etc.

The scripts use the pexpect module to login to remote systems and do
sysadmin tasks (e.g. reset passwords).  This works like a charm in console

The gui uses a QThread to poll logQueue (logQueue.get()).  When it gets
something, it creates a QCustomEvent and sets the data portion using the
data read from the logQueue.  I have a customEvent method in my application
which grabs the data from the customEvent and processes it accrodingly
(writing output to a QTable).

The gui locks up after an arbitrary number of rows have been inserted in the
QTable.  It is not consistent.  Sometimes it does not lock at all.

I have a non-threaded set of the command line tools which run perfectly with
the gui.


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