UnboundLocalError: local variable 'colorIndex' referenced

[Rick Zantow]

silverburgh.meryl at gmail.com wrote in news:1140987642.195734.187540
@t39g2000cwt.googlegroups.com:

> Can you please tell me what is the meaning this error in general?
> 
>  UnboundLocalError: local variable 'colorIndex' referenced before
> assignment
> 
> In my python script,
> I have a variable define and init to 0, like this
> colorIndex  = 0
> 
> and in one of my functions,  I increment it by 1
> def myFunc 
>    colorIndex += 1
> 
> 

It's a scoping issue. Within myFunc, if colorIndex receives a value 
(that is, if you assign something to it, as you do here), Python 
requires a local variable, one known within the scope of function. If 
you had only *read* the variable (x = colorIndex, for instance), then 
Python will first look for a local variable, and, finding none, will 
then look for a global variable, which it would find in this case. The 
net effect of all this is a common gotcha for new Python users: the 
'colorIndex' that is assigned to  within myFunc is *not* the same as the 
one you assigned 0 to earlier; they just happen to share the same name. 

You can get around this in various ways. One is to declare the variable 
in myFunc, like this:
def myFunc
    	global colorIndex
    	colorIndex += 1
    	...

-- 
rzed