A unique instance of Python GUI program

[akineko]

Hello everyone,

This may not be a Python specific challenge.
I have a GUI program written in Python + Tkinter.
It works very well.

Now, I would like to start it from a shell script.
As my GUI program includes a server, it should not have more than one
instance.
Is there any easy way to check if another instance of the program is
already running.

I vaguely remember that Windows programming provides a way to check.

A platform independent approach would be nice but a solution for X is
sufficient for my application.

Any comments will be greatly appreciated.

Best regards,
Aki Niimura

[Tim Golden]

Re: A unique instance of Python GUI program

akineko wrote:

This may not be a Python specific challenge.
I have a GUI program written in Python + Tkinter.
It works very well.
>
Now, I would like to start it from a shell script.
As my GUI program includes a server, it should not have more than one
instance.
Is there any easy way to check if another instance of the program is
already running.
>
I vaguely remember that Windows programming provides a way to check.
>
A platform independent approach would be nice but a solution for X is
sufficient for my application.

I swear this question's been asked twice this month already.
Is there a convention going on of one-instance-only application writers?

Have a look at:

http://mail.python.org/pipermail/python-list/2008-August/505958.html

http://mail.python.org/pipermail/python-list/2008-August/505992.html

http://mail.python.org/pipermail/python-list/2008-August/505850.html

or just search the mailing lists for various previous
discussions:

http://www.google.com/search?q=site%3Amail.python.org+application+single+instance

(or similar queries)

TJG

[Georg Altmann]

Re: A unique instance of Python GUI program

akineko schrieb:

Hello everyone,
>
This may not be a Python specific challenge.
I have a GUI program written in Python + Tkinter.
It works very well.
>
Now, I would like to start it from a shell script.
As my GUI program includes a server, it should not have more than one
instance.
Is there any easy way to check if another instance of the program is
already running.
>
I vaguely remember that Windows programming provides a way to check.

On windows a mutex does the job, see CreateMutex in the windows api.

A platform independent approach would be nice but a solution for X is
sufficient for my application.

I'm not familiar with Tkinter - you might want to check if it supports
mutexes. Though I'm not sure if mutexes are cross-process (system wide)
on all platforms.

Regards
Georg

[Larry Bates]

Re: A unique instance of Python GUI program

akineko wrote:

Hello everyone,
>
This may not be a Python specific challenge.
I have a GUI program written in Python + Tkinter.
It works very well.
>
Now, I would like to start it from a shell script.
As my GUI program includes a server, it should not have more than one
instance.
Is there any easy way to check if another instance of the program is
already running.
>
I vaguely remember that Windows programming provides a way to check.
>
A platform independent approach would be nice but a solution for X is
sufficient for my application.
>
Any comments will be greatly appreciated.
>
Best regards,
Aki Niimura

Here is a recipe:

http://code.activestate.com/recipes/474070/

-Larry

[akineko]

Re: A unique instance of Python GUI program

On Sep 16, 1:58 am, Tim Golden <m...@timgolden .me.ukwrote:

I swear this question's been asked twice this month already.

Thank you very much for many pointers.
I'm awfully sorry for posting something that is already answered in
the past.
I tried to find answers to my problem using "unique instance" as a
keyword.
I guess I should have used "single instance" or "one instance",
instead.
I will try to be more careful before posting.

Thank you.
Aki Niimura

[Tim Golden]

Re: A unique instance of Python GUI program

akineko wrote:

On Sep 16, 1:58 am, Tim Golden <m...@timgolden .me.ukwrote:

>I swear this question's been asked twice this month already.

>
>
Thank you very much for many pointers.
I'm awfully sorry for posting something that is already answered in
the past.

I was more amused than annoyed. Don't let my tone put
you off. In any case, searching is all too often a
question of knowing what the answer is so you can
search for it!

TJG

[akineko]

Re: A unique instance of Python GUI program

Again, thank you for many postings to my question.
I have reviewed solutions provided.
Well, I like the named Mutex solution under Windows.
That is a clean and straight-forward approach to the challenge.
(I cannot believe that I'm saying good thing about Windows ;-) )

Unfortunately, I'm living in Unix realm ;-)

None of solutions for Unix are appealing to me.
But they must be "the" solution for the challenge as well-established
software uses those solutions.

Now, I'm wondering.
As my program is a GUI (Tkinter) software.
Is it possible to set a known value to X11 or Tk property through
Tkinter so that another instance of the program can check if such
property is set?

Of course, I know this scheme has a flaw. If one instance uses another
logical display, then such property is probably not shared.
But for my usage, it is logically possible but not likely.

I checked my Tkinter book and found the following function.
winfo_interps(d isplayof=0)

This returns a list of all Tk-based applications currently running on
the display.

When I tried, I got the following:

>>root.winfo_in terps()

('tk #3', 'tk #2', 'tk')

But I couldn't find a way to set a specific name to the Tcl
interpreter.

As I'm not an expert of Tcl/Tk and X11, I probably overlooked other
functions that may do what I need.

Any comments, suggestions on this?
Maybe this can provide a platform independent way to ensure that only
single instance is running.

Thank you for your attention.

Best reagrds,
Aki Niimura

[r0g]

Re: A unique instance of Python GUI program

akineko wrote:

Again, thank you for many postings to my question.
I have reviewed solutions provided.
Well, I like the named Mutex solution under Windows.
That is a clean and straight-forward approach to the challenge.
(I cannot believe that I'm saying good thing about Windows ;-) )
>
Unfortunately, I'm living in Unix realm ;-)
>
None of solutions for Unix are appealing to me.
But they must be "the" solution for the challenge as well-established
software uses those solutions.
>
Now, I'm wondering.
As my program is a GUI (Tkinter) software.
Is it possible to set a known value to X11 or Tk property through
Tkinter so that another instance of the program can check if such
property is set?
>
Of course, I know this scheme has a flaw. If one instance uses another
logical display, then such property is probably not shared.
But for my usage, it is logically possible but not likely.
>
I checked my Tkinter book and found the following function.
winfo_interps(d isplayof=0)
>
This returns a list of all Tk-based applications currently running on
the display.
>
When I tried, I got the following:

>>>root.winfo_i nterps()

('tk #3', 'tk #2', 'tk')
>
But I couldn't find a way to set a specific name to the Tcl
interpreter.
>
As I'm not an expert of Tcl/Tk and X11, I probably overlooked other
functions that may do what I need.
>
Any comments, suggestions on this?
Maybe this can provide a platform independent way to ensure that only
single instance is running.
>
Thank you for your attention.
>
Best reagrds,
Aki Niimura

I know it's a hack but couldn't you just open a specific UDP socket and
leave it dangling til your program exits, then if a new instance can't
open that same socket it can gracefully abort? If your program dies the
socket will be freed up again by the OS yes?

Just a thought.

Roger.

[Grant Edwards]

Re: A unique instance of Python GUI program

On 2008-09-16, akineko <akineko@gmail. comwrote:

This may not be a Python specific challenge. I have a GUI
program written in Python + Tkinter. It works very well.
>
Now, I would like to start it from a shell script. As my GUI
program includes a server, it should not have more than one
instance. Is there any easy way to check if another instance
of the program is already running.
>
I vaguely remember that Windows programming provides a way to
check.

On unix the solution is usually a lockfile placed in a
predefined location. Other people use a socket, but that's a
bit more susceptible to namespace collisions with unrelated
programs.

A platform independent approach would be nice but a solution
for X is sufficient for my application.

I don't see what X has to do with it.

Any comments will be greatly appreciated.

This question is asked and answered about once a week, and I'm
always surprised at how frequently it comes up. I've been
doing sw development for decades and apart from Unix system
daemons, I don't remember ever needing to prevent multiple
instances of an application from running. Can somebody lend me
a clue as to why this question comes up so often? There can't
be that many people writing Unix daemons in Python (and if they
were, they'd probably already know about lockfiles).

Just curious...

--
Grant Edwards grante Yow! Is something VIOLENT
at going to happen to a
visi.com GARBAGE CAN?