Meta classes - real example

[Chris Angelico]

On Tue, Oct 18, 2016 at 3:03 AM, Mr. Wrobel <mr at e-wrobel.pl> wrote:
> Hi,
>
> I am looking for an example of metaclass usage. Especially I am interestet
> in manipulating instance variables, for example:
>
> My class:
> class MrMeta(type):
>         pass
>
> class Mr(object):
>         __metaclass__ = MrMeta
>
>         def __init__(self):
>                 self.imvariable = 'Zmienna self'
>
>         def aome method(self):
>                 print 'I am in instance'
>
> So in general, I would like to create a mechanism, that is changing value
> for self.imvariable to capital letters and this should be included in my
> metaclass called MrMeta(type).
>
> Can you guide me please?

Are you sure you can't just use a descriptor, such as @property?

class Mr(object):
    @property
    def imvariable(self):
        return self._imvariable
    @imvariable.setter
    def imvariable(self, value):
        self._imvariable = str(value).upper()

ChrisA