Question

This question is about Python inheritance but is explained with a Django example, this should’t hurt though.

I have this Django model, with Page and RichText models as well:

class Gallery(Page, RichText):
    def save(self, *args, **kwargs):
        # lot of code to unzip, check and create image instances.
        return "something"

I’m only interested in using the save method in another class.

A solution could be:

class MyGallery(models.Model):
    def save(self, *args, **kwargs):
        # here goes the code duplicated from Gallery, the same.
        return "something"

I’d like to avoid the code duplication and also I’m not interested in inheriting members from Page and RichText (so I don’t want to do class MyGallery(Gallery):. If it would be legal I’d write something like this:

class MyGallery(models.Model):
    # custom fields specific for MyGallery
    # name = models.CharField(max_length=50)
    # etc

    def save(self, *args, **kwargs):
        return Gallery.save(self, *args, **kwargs)

But it won’t work because the save() in Gallery expects an instance of Gallery, not MyGallery.

Any way to “detach” the save() method from Gallery and use it in MyGallery as it were defined there?

EDIT:

I forgot to say that Gallery is given and can’t be changed.

Answer 1

You can access the __func__ attribute of the save method:

class Gallery(object):
    def save(self, *args, **kwargs):
        return self, args, kwargs

class MyGallery(object):
    def save(self, *args, **kwargs):
        return Gallery.save.__func__(self, *args, **kwargs)
    # or 
    # save = Gallery.save.__func__

mg = MyGallery()
print mg.save('arg', kwarg='kwarg')
# (<__main__.MyGallery object at 0x04DAD070>, ('arg',), {'kwarg': 'kwarg'})

but you’re better off refactoring if possible:

class SaveMixin(object):
    def save(self, *args, **kwargs):
        return self, args, kwargs

class Gallery(SaveMixin, object):
    pass

class MyGallery(SaveMixin, object):
    pass

or

def gallery_save(self, *args, **kwargs):
    return self, args, kwargs

class Gallery(object):
    save = gallery_save

class MyGallery(object):
    save = gallery_save