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- Astropy v1.1.1 »
- Astropy Core Package Utilities (`astropy.utils`) »
- sharedmethod

# sharedmethod

class `astropy.utils.decorators.``sharedmethod`

  Bases: `classmethod`

  This is a method decorator that allows both an instancemethod and a `classmethod` to share the same name.

  When using `sharedmethod` on a method defined in a class’s body, it may be called on an instance, or on a class. In the former case it behaves like a normal instance method (a reference to the instance is automatically passed as the first `self` argument of the method):

      >>> class Example(object):
      ...     @sharedmethod
      ...     def identify(self, *args):
      ...         print('self was', self)
      ...         print('additional args were', args)
      ...
      >>> ex = Example()
      >>> ex.identify(1, 2)
      self was <astropy.utils.decorators.Example object at 0x...>
      additional args were (1, 2)

  In the latter case, when the `sharedmethod` is called directly from a class, it behaves like a `classmethod`:

      >>> Example.identify(3, 4)
      self was <class 'astropy.utils.decorators.Example'>
      additional args were (3, 4)

  This also supports a more advanced usage, where the `classmethod` implementation can be written separately. If the class’s metaclass has a method of the same name as the `sharedmethod`, the version on the metaclass is delegated to:

      >>> from astropy.extern.six import add_metaclass
      >>> class ExampleMeta(type):
      ...     def identify(self):
      ...         print('this implements the {0}.identify '
      ...               'classmethod'.format(self.__name__))
      ...
      >>> @add_metaclass(ExampleMeta)
      ... class Example(object):
      ...     @sharedmethod
      ...     def identify(self):
      ...         print('this implements the instancemethod')
      ...
      >>> Example().identify()
      this implements the instancemethod
      >>> Example.identify()
      this implements the Example.identify classmethod