Callback functions arguments
nomail at invalid.com
Tue Oct 28 08:35:01 CET 2014
"Peter Otten" <__peter__ at web.de> a écrit dans le message de
news:mailman.15231.1414399974.18130.python-list at python.org...
Tanks for you answer
> Python doesn't "know" it has to pass an argument, it just does it. Change
> the callback to
> def maj():
> print("no args")
> and you'll get an error. If I were to guess
Yes you are right. I got an error:
TypeError: maj() takes 0 positional arguments but 1 was given
OK, but i still find very strange the choice of Python's designers to
make the Scale behaves like that.
The position of the scale is in variable Valeur (StringVar()) which
cold be read/write from anywhere, so it is not necessary to pass
this variable as an argument to the call back function.
If you are looking at the SpinBox widget, in example 4 in the
same web site:
boite = Spinbox(Mafenetre,from_=0,to=10,increment=0.5, \
with the callback function "carre"
""" Calcul du carré """
Resultat.set("Carré = "+str(float(Valeur.get())**2))
you can notice that carre function has no arguments. The value
in the SpinBox is catched with Valeur variable.
So SpinBox and Scale behaves differently. It is strange.
> you probably are misled by the 'command=maj' part in the above line.
no, I understood this mechanism
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