Unbound Local error --???

[Gabriel Genellina]

En Tue, 26 Jun 2007 21:48:50 -0300, hari sirigibathina  
<hari.siri74 at gmail.com> escribió:

> -Calling a method say aMethod() from another method where i mistakenly
> initialised a variable with name same as the called method like aMethod =
> 'string'. When i run this py script triggered "Unbound Local error".
> can any  one explain me whats going here ? curios to learn from my  
> mistake
> :)

A simple example:

>>> def f():
...   x = a + 1
...   a = 3
...
>>> f()
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "<stdin>", line 2, in f
UnboundLocalError: local variable 'a' referenced before assignment

That means:
  1) Python knows that variable "a" is local (because you assign 3 to it  
later)
  2) But you have not assigned anything to it yet.

>>> def g():
...   x = a + 1
...
>>> g()
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "<stdin>", line 2, in g
NameError: global name 'a' is not defined

This time, "a" is not local, and not found in the global namespace either.  
The message tells you that it was looking for a global variable, and could  
not find it.

-- 
Gabriel Genellina