encapsulating a global variable

[Rhodri James]

On 25/02/2020 12:38, BlindAnagram wrote:
> I would appreciate advice on whether it is possible to avoid the use of
> a global variable used in a function by encapsulating it in a class
> without maaking any changes to the call interface (which I cannot change).
> 
> I have:
> 
> ----------------
> seen = dict()
> 
> def get_it(piece):
>     ...
>     return seen[piece]
> ----------------
> 
> and I am wondering if it is possible to use a class something like
> 
> ----------------
> class get_it(object):
> 
>    seen = dict()
> 
>    def __call__(piece):
>      return seen[piece]
> ----------------
> 
> to avoid the global variable.

I wouldn't.  Calling the class name creates an instance of the class, so 
won't actually do what you want.  You could rewrite the class and create 
an instance to call instead:

class GetIt:
   seen = dict()

   def __call__(self, piece):
     return GetIt.seen[piece]

get_it = GetIt()

but then you have a global class instance hanging around, which is not 
actually any better than a global dictionary.


-- 
Rhodri James *-* Kynesim Ltd