map -> class instance

[Christophe Delord]

self.x=y is a call to self.__setattr__, so if you write self.x=y in __setattr__ it is an infinite recursion.
(see http://www.python.org/doc/current/ref/attribute-access.html#l2h-112)

in __setattr__, self.m[key]=val may be written self.__dict__['m'][key]=val
in __init__, self.m=m may be written self.__dict__['m']=m


$ cat map2class.py
class Map2Class:
    def __init__(self,m):
        self.__dict__['m'] = m

    def __getattr__(self, key):
        return self.m[key]

    def __setattr__(self, key, val):
        self.__dict__['m'][key] = val

    def __delattr__(self, key):
        if self.m.has_key(key):
            del self.m[key]

m = {'first' : 'John',
     'last' : 'Hunter',
     'age' : 34}

c = Map2Class(m)
print c.first, c.last, c.age
$ python map2class.py
John Hunter 34
$


Christophe.


On Wed, 12 Jun 2002 16:49:32 -0500
John Hunter <jdhunter at nitace.bsd.uchicago.edu> wrote:

> 
> I want to convert dictionary instances to instances of a class that
> has the keys of the map as attributes.  I naively tried this:
> 
> class Map2Class:
>     def __init__(self,m):
>         self.m = m
> 
>     def __getattr__(self, key):
>         return self.m[key]
> 
>     def __setattr__(self, key, val):
>         self.m[key] = val
> 
>     def __delattr__(self, key):
>         if self.m.has_key(key):
>             del self.m[key]
> 
> m = {'first' : 'John',
>      'last' : 'Hunter',
>      'age' : 34}
> 
> c = Map2Class(m)
> print c.first, c.last, c.age
> 
> But got an infinite recursion:
> 
> ~/python/test $ python map_to_class.py 
> Traceback (most recent call last):
>   File "map_to_class.py", line 20, in ?
>     c = Map2Class(m)
>   File "map_to_class.py", line 3, in __init__
>     self.m = m
>   File "map_to_class.py", line 8, in __setattr__
>     self.m[key] = val
>   File "map_to_class.py", line 5, in __getattr__
>     return self.m[key]
>   File "map_to_class.py", line 5, in __getattr__
>     return self.m[key]
>         [snip ... lots more line fivers ]
> 
> Is there a better/right way to do what I want?
> 
> Thanks,
> John Hunter


-- 

(o_   Christophe Delord                   _o)
//\   http://christophe.delord.free.fr/   /\\
V_/_  mailto:christophe.delord at free.fr   _\_V