Application console for Tkinter program?

[Christian Gollwitzer]

Am 05.03.16 um 11:15 schrieb Terry Reedy:
> On 3/5/2016 2:52 AM, Christian Gollwitzer wrote:
>> is there an easy way to add an application console to a Tkinter program?
>
> Right now, you should turn the question around.

so this means no, right?

> Is there an easy way to
> run a tkinter program within an interactive console?  Answer: yes, two
> ways, after removing the runshell stuff and mainloop call*.
>
> 1. Call your program mytk.py.  In your system console, run 'python -i
> myth.py'.  When the code ends, control passes to the console running
> python.  Statements like 'print(nvar.get())' will be executed in the
> main namespace of the still running program.

well yes, this does work, but I should have explained why I want it the 
other way round. We have an in-house tool which is used to manipulate 
images. During production use, at some point you think "and now if I 
could just save the image that I see on screen into a PNG file". You 
know exactly that MyViewer.image is the thing that contains what you 
need, if only you had a way to tell it 
'MyViewer.image.save("somewhere.png")'. At this point, you haven't 
started the program from an interactive python. Always running the tool 
from ipython or idle means there are useless windows hanging around, but 
if you close them, your pogram goe away. To make it even more 
complicated, the deployed version of the tool uses pyinstaller to be 
safe from environment changes.

Of course, I could pack some text widget somewhere and fiddle a few 
bindings to make it do this with eval(), but a good REPL has history, 
autocompletion, syntax highlighting.... you get it. I had simply hoped, 
since idle is written in Tkinter, that it could be reused for that purpose.

For pure Tcl/Tk, there is tkcon which can do exactly this and I use it 
in similar tools writtin in Tcl/Tk. I can run it via Tk.eval(), but I 
couldn't find a way to call back into Python coming from the Tkinter 
interpreter, and obviously autocompletion and syntax highlighting do not 
work well.

>> For instance, can you embed IDLE into a program such that when a button
>> is pressed, it pops up a REPL window where the running program can be
>> examined?
>
> If the REPL window is defined in an imported module, the problem is
> linking the main namespace of the tkinter program with the REPL loop in
> such a way that commands entered into the REPL are executed in the main
> module, not in the REPL module.

I'm happy to pass the main module as an argument to REPLInit().

>> 2) If you click the Shell button twice, it locks up the program, because
>> main() obviously starts it's own mainloop
>
> IDLE executes user code in a separate process, linked by sockets, so
> that execution of IDLE GUI code and user code do not interfere with each
> other.

Ahhh - OK this makes sense in the general case, but not for a console 
where you *want* your REPL to perform surgery on the main program.

> I would like to refactor IDLE so that the Shell window
> ...
> It might be possible to adapt such a component as an embedded console.
> An imported frame should not interfere with the main-module code or code
> in other modules.  The main problems are a) namespace linkage (mentioned
> before),


> b) the need for sys.stdin/out/err to not be None,

tkcon solves this be redirecting stdin/stdout/stderr to functions which 
write to the console window.

> and c) for
> capturing exceptions in code entered in the console, so as to not crash
> the main program.


For Python exceptions I see no problem - the eval must simply be 
properly wrapped in try..except and the traceback is redirected to the 
console. If a C level exception occurs, this will crash everything, but 
that's OK.

	Christian