[Python-ideas] Simple class initialization

[Arnaud Delobelle]

On 16 Apr 2011, at 12:50, Adam Matan wrote:

> 0. Abstract
> ===========
> 
> A class initialization often begins with a long list of explicit variable 
> declaration statements at the __init__() method. This repetitively copies 
> arguments into local data attributes.
> This article suggests some semi-automatic techniques to shorten and clarify 
> this code section. Comments and responses are highly appreciated.

Following a discussion on c.l.python, I posted a recipe on ActiveState a while ago that attempted to deal with this issue:

    http://code.activestate.com/recipes/551763-automatic-attribute-assignment/

From the docstring:

    """
    autoassign(function) -> method
    autoassign(*argnames) -> decorator
    autoassign(exclude=argnames) -> decorator
    
    allow a method to assign (some of) its arguments as attributes of
    'self' automatically.  E.g.
    
    >>> class Foo(object):
    ...     @autoassign
    ...     def __init__(self, foo, bar): pass
    ... 
    >>> breakfast = Foo('spam', 'eggs')
    >>> breakfast.foo, breakfast.bar
    ('spam', 'eggs')
    
    To restrict autoassignment to 'bar' and 'baz', write:
    
        @autoassign('bar', 'baz')
        def method(self, foo, bar, baz): ...

    To prevent 'foo' and 'baz' from being autoassigned, use:

        @autoassign(exclude=('foo', 'baz'))
        def method(self, foo, bar, baz): ...
    """

-- 
Arnaud