Tkinter & Python: how to get the return of a call associated to an event on my gui
egbert at bork.demon.nl
Sat Jun 22 13:57:15 EDT 2002
A callback may do something, but it does not return anything,
at least not something you may use. I suppose that you need 'global',
ie an export of a name from within a function (the local namespace)
to the surrounding global one: the namespace of the module in which
the function is defined. I think the line 'global result' in your
callback will help.
As long as you stay within one class-instance, you can solve it in
another way: let your callback produce a 'self.result', which is
available in the whole class-instance.
Things become interesting when you have two classes, A and B,
and A needs the data that will be collected by a gui in B.
I call it interesting because I am still struggling with it.
A and B should agree on the layout of the data structure that goes
from B to A, but how B collects these data, from which entries or
canvases, is entirely his own business. In the same way: B knows
nothing of the way A handles these data.
First the solution, and then some explanations.
# build a gui ...
bouton = Button( ....., command=callback)
# collect the gui-data in retour_list,
# and probably close this b-gui.
b = B( ..., callback=self.sign)
self.data_list = b.retour()
# do something usefull with self.data_list
# exit (button) the application
Within the usual Tkinter loop you start this with:
a = A()
A passes in an argument the name of a callback to B.
This callback ('sign') is a method of A.
The chain of activities is started by the button-push in B
that activates the callback in A.
The callback sends a message ('retour') to B to collect
and return the data, and A processes them.
How B collects the data is hidden in 'retour', and what A
does with them is hidden in 'process_data'.
Now I have two questions:
am I making things much too complicated, or
does some standard pattern solve this problem in a better way ?
Egbert Bouwman - Keizersgracht 197 II - 1016 DS Amsterdam - 020 6257991
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