I don't see a conflict between encouraging accessors and making duplicate methods/functions. If you want duplicate method/functions, you can totally do that on an accessor class:

``` python import functools import xarray

@xarray.register_dataarray_accessor('custom') class CustomAccessor(object): def init(self, data_array): self._data_array = data_array

def patch_custom(func): @functools.wraps(func) def method(accessor, args, kwargs): return func(accessor._data_array, args, **kwargs) setattr(CustomAccessor, func.name, method) return func

@patch_custom def square(data_array): return data_array ** 2

xarray.DataArray([1, 2, 3], dims='x').custom.square()

<xarray.DataArray (x: 3)>

array([1, 4, 9])

Coordinates:

* x (x) int64 0 1 2

```

If you really desire, you can even make method-like accessors by adding a __call__ method, e.g.,

@xarray.register_dataarray_accessor('square') class Square(object): def __init__(self, data_array): self._data_array = data_array def __call__(self): return self._data_array ** 2

or even simpler

@xarray.register_dataarray_accessor('square') def square_accessor(data_array): def square(): return data_array ** 2 return square

I would definitely discourage writing too many of such methods, though.

Finally, it seems like the simplest solution to your concern about needing methods for Dataset.apply would be to register an accessor for Dataset as well, with register_dataset_accessor.