Beginner's scoping question

[Ivo Woltring]

On 10 Nov 2004 12:40:34 -0800, contact at alanlittle.org (Alan Little)
wrote:

>a=1
>b=[]
>class C():
is should be...
class C: # whithout the ()
>   def __init__(self):
>      a=2
>      b.append(3)
>
>c = C()
>
>print b
># [3]
>
># but ...
>print a
># 1
>
>???


a=1
b=[]
class C:
   def __init__(self):
      global a                         # !!!!!!!!!!!
      a=2
      b.append(3)

c = C()

print b
# [3]

# but ...
print a
# 2

a in the class is a local to that class and because it in not assiged
to self.a it is also not normally addressable outside the class
if you want to change the already existing global a you have to
declare it global (see code)

You try to append to a non-existing local variable b.
Python first tries the local() namespace and then the global()
it finds b in the global namespace and appends the value.

cheerz,
Ivo