[Python-ideas] Syntax for making stuct / record / namedtuples

[Arnaud Delobelle]

On 21 Oct 2009, at 16:56, Bruce Leban wrote:

> Reading your code I have no idea what these lines mean
>
>
>     autoassign(function) -> method
>     autoassign(*argnames) -> decorator
>     autoassign(exclude=argnames) -> decorator
>
> Reading the code, what I *think* this does
>
> """Decorator that assigns all function parameters to attributes of  
> the class.
> You can specify a list of parameters to process or a list of  
> parameters to exclude.
> Given another function, does something complicated that belongs in  
> another recipe.
> """
>

I don't understand that last sentence.

> I'm only half-joking. It's not obvious what that function parameter  
> does and you don't give any examples of it's use.

I give two examples.  One in the docstring (first example), the other  
one in the tests below the definition of the decorator (class Test2).

> Just reading the code with unrelated assignments grouped together  
> was confusing enough -- definitely not my coding style.

Sorry I confused you :)

>
> More importantly not at all clear why this is better than
>
>     self.__dict__.update(locals())
>

It's not a very nice construct. And it doesn't work as is:

 >>> class Foo(object):
...     def __init__(self, a, b, c):
...             self.__dict__.update(locals())
...
 >>> foo=Foo(1, 2, 3)
 >>> foo.self
<__main__.Foo object at 0x10048c790>

Probably not what was intended...  So you can write something like:

 >>> class Foo(object):
...     def __init__(self, a, b, c):
...             self.__dict__.update(((n, v) for (n, v) in locals 
().items() if n!='self'))
...
 >>> foo=Foo(1, 2, 3)
 >>> foo.self
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute 'self'

But that reads even worse.

Also, it's a bit more versatile.

-- 
Arnaud