nested classes

[Skip Montanaro]

    Bjorn> But that's an implementation detail only, since it works
    Bjorn> perfectly for functions:

    Bjorn>   def foo():
    Bjorn>       foo()

Only because at the point that foo calls itself recursively, the definition
of foo is in the module's global symbol table, assuming foo is def'd at the
module scope.  If foo is nested inside another function, it can't call
itself directly without some help from the function it's enclosed in.

Before nested scopes, the following won't work:

    % python
    Python 2.1.1a1 (#10, Jun  8 2001, 14:37:03) 
    [GCC 2.96 20000731 (Linux-Mandrake 8.0 2.96-0.48mdk)] on linux2
    Type "copyright", "credits" or "license" for more information.
    >>> if 1:
    ...     def bar():
    ...         def foo(i=0):
    ...             if i < 10:
    ...                 foo(i+1)
    ...         foo()
    ...     bar()
    ... 
    <stdin>:2: SyntaxWarning: local name 'foo' in 'bar' shadows use of 'foo' as global in nested scope 'foo'
    Traceback (most recent call last):
      File "<stdin>", line 7, in ?
      File "<stdin>", line 6, in bar
      File "<stdin>", line 5, in foo
    NameError: global name 'foo' is not defined
    >>> from __future__ import nested_scopes
    >>> if 1:
    ...     def bar():
    ...         def foo(i=0):
    ...             if i < 10:
    ...                 foo(i+1)
    ...         foo()
    ...     bar()
    ... 
    >>> 

When defining a class, the code within the class's scope is executed
immediately, before a class object has been bound to the class's name.

-- 
Skip Montanaro (skip at pobox.com)
(847)971-7098