Op 24-06-13 21:47, pablobarhamal...@gmail.com schreef:
Hi there! I'm quite new to programming, even newer in python (this is actually
the first thing I try on it), and every other topic I've seen on forums about
my problem doesn't seem to help.
So, the following lines are intended to draw a white square (which it does),
turn it to blue when you click on it, and back to white when you click on it
again (and so on). Here's what I wrote (python 3 syntax):
from tkinter import *
root = Tk()
root.geometry("500x500")
w = Canvas(root, width=500, height=500)
w.pack()
coords = (x1, y1, x2, y2) = (100, 100, 200, 200)
rect = w.create_rectangle(coords, fill="white")
isWhite = True
def change(event):
if event.x> x1 and event.x< x2 and event.y> y1 and event.y< y2:
if isWhite:
w.itemconfig(rect, fill="blue")
isWhite = False
else:
w.itemconfig(rect, fill="white")
isWhite = True
w.bind("<Button-1>", change)
root.mainloop()
The problem occurs when clicking on the white square. The following error
appears:
"if isWhite:
UnboundLocalError: local variable 'isWhite' referenced before assignment"
However, the isWhite variable is clearly defined at "True" a few lines before.
No it is not.
In Python, when you assign to a variable within a function, that
variable will be treated as a local variable. If you have a global
variable with the same name, that global variable will just for
the duration of the function become inaccessible.
The quick solution in this case is to include a global statement.
Something like
def change(event)
global isWhite
...
--
Antoon Pardon
--
http://mail.python.org/mailman/listinfo/python-list
