issue_comments

:+1:

We might want to discourage using this to add methods to the DataArray / Dataset namespace, though.

Would it be worth adding @keewis' examples to the accessor documentation?

@keewis, thanks for the suggestions. Both seem reasonable.

In your first example, if you wanted to prohibit obj.weighted.sum(dim), you could just check for self._weight in sum(). Though I suppose it would be nice to be able to have the interpreter enforce the requirement and not have to do an explicit check in every method.

not sure if you really should use accessors to do that; having a function return a wrapper object might be enough.

Then again, an accessor is a slightly modified version of a property so you can just make your object callable by defining __call__: ```python @xr.register_dataarray_accessor("weighted") class Weighted: def init(self, xarray_obj): self._obj = xarray_obj self._weight = None

def __call__(self, weight):
    self._weight = weight

def sum(self, dim):
    return "weighted sum"

this does allow calling `obj.weighted.sum(dim)`, so instead you can use:python In [2]: class Weighted: ...: def init(self, obj, weight): ...: self._obj = obj ...: self._weight = weight ...:
...: def sum(self, dim): ...: return f"weighted sum over {dim} and with weight {self._weight}" ...:
...: @xr.register_dataarray_accessor("weighted") ...: def weighted(obj): ...: def wrapped(weight): ...: return Weighted(obj, weight) ...: return wrapped ...:
...: da = xr.DataArray(data=range(5), dims="x") ...: da.weighted(5).sum(dim="x") Out[2]: 'weighted sum over x and with weight 5' ```

Edit: the warning about a overridden attribute was the result of rerunning the code without restarting the interpreter