Running a GUI program haults the calling program (linux)

[Kryptxy]

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> -------- Original Message --------
> Subject: Re: Running a GUI program haults the calling program (linux)
> Local Time: 26 September 2017 12:09 PM
> UTC Time: 26 September 2017 06:39
> From: cs at cskk.id.au
> To: Kryptxy <kryptxy at protonmail.com>
> python-list <python-list at python.org>
>
> On 25Sep2017 20:38, Kryptxy <kryptxy at protonmail.com> wrote:
>>I want to run a GUI program (transmission-gtk) from python. This is what I do:
>>
>>import subprocess
>>subprocess.Popen(["transmission-gtk", link], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
>>
>>Where `link` is some magnetic link.
>>
>>This command opens transmission-gtk, but it haults the calling program, and keeps the terminal busy till the time GUI is running.
>>As soon as GUI is closed, the control goes back to the program.
>
> I do not believe this is all your code. Please post a _complete_ example.
>
> Popen dispatches a process. It does not wait for it to terminate. GUI programs
> are not special. Therefore, if your calling python program is blocking, it is
> blocking somewhere other that this line of code. Please show us where.
>
> Consider putting print() calls through your code to locate where your program
> stalls.
>
> Cheers,
> Cameron Simpson <cs at cskk.id.au> (formerly cs at zip.com.au)

Here -

p = subprocess.Popen(['transmission-gtk', link], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
output, error = p.communicate()
error = error.decode('utf-8')
output = output.decode('utf-8')
if error != '':
    print("\nUnable to load torrent.")
else:
    print("Torrent added successfully!")

Here, transmission-gtk is opened and the program haults (at subprocess.Popen() statement).
When I close the GUI window, I get the message "Unable to load torrent".

Error message I get:
`Unable to parse nameserver address 8.8.8.8,`
`(transmission-gtk:3982): GLib-CRITICAL **: g_file_test: assertion 'filename != NULL' failed`