> def handler(event):
> if buttonpressed == 1 :
> /#if the mousebutton is pressed and moved, circles should
> appear, but they do not/
> can.create_oval(event.x-r, event.y-r, event.x+r, event.y+r,
> fill="orange")
> lab.config(text='buttonpressed=' + str(buttonpressed) )
The variables of functions are normally independent of each other. That
is, if I have a function square():
##############
def square(x):
y = x * x
return y
##############
and if I have a function that uses square that itself has a 'y' variable,
I should not see interference:
##############
def test():
y = 17
print "square of y is", square(y)
print "y itself is", y
##############
This black-boxing is what allows us to write and reuse functions with
reckless abandon: their innards are meant not to interact with one
another. This is a feature that you usually want to have.
But for your purposes, you want some controlled form of leakage. Use
'global' for this purpose by declaring the shared variable at the head of
your functions. Compare the results above to the ones below:
#####################################
def square(x):
global y
y = x * x
return y
def test():
global y
y = 17
print "square of y is", square(y)
print "y itself is", y
#####################################
There's terse reference material here about global:
http://www.python.org/doc/ref/global.html#l2h-558
It's idiomatic programming practice to limit the use of 'global' to
situations where it's necessary; using it in an uncontrolled way leads to
code that's difficult to read or reason with. There are more sophsticated
ways to share variables between functions. That being said, though, the
'global' mechanism will probably be simplest for your purposes.
Good luck to you!
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