issue_comments

Hi. Ok Sorry. Had no idea what I was doing. So I hope I fixed it, the way you wanted. I added a test-routine test_binary_ops_keep_attrs Created a new pull request, as I could not reopen the old one

Hi @MBlaschek, almost there! You'll need to open your pull request in this repository :).

You'll also need to add some tests to make sure your changes keep working as the code is updated in the future. E.g. https://github.com/pydata/xarray/blob/0d6056e8816e3d367a64f36c7f1a5c4e1ce4ed4e/xarray/tests/test_variable.py#L1533

@MBlaschek This might help: https://help.github.com/articles/proposing-changes-to-your-work-with-pull-requests/ . You'd start by creating a fork, then a branch with your changes, push your changes to github and then initiate a pull request.

Not sure what a PR is. (Sorry I'm not that advanced in coding)

PR is a pull-request! If you can open a PR with your code, we can merge it to the repo. Would be greatly appreciated from xarray, and you'd be an xarray contributor. Let us know if we can help guide you through the mechanics.

Thanks for the quick reply. Not sure what a PR is. (Sorry I'm not that advanced in coding) I figure, from code you have been using at other places, something like that ```python @staticmethod def _binary_op(f, reflexive=False, **ignored_kwargs): @functools.wraps(f) def func(self, other): if isinstance(other, (xr.DataArray, xr.Dataset)): return NotImplemented self_data, other_data, dims = _broadcast_compat_data(self, other) # Add Attributes here ? keep_attrs = _get_keep_attrs(default=False) attrs = self._attrs if keep_attrs else None

    with np.errstate(all='ignore'):
        new_data = (f(self_data, other_data)
                    if not reflexive
                    else f(other_data, self_data))
    result = Variable(dims, new_data, attrs=attrs)
    return result
return func

``` should do the trick. Right. I cloned the recent version and tried out the new code. It works! :)

When the option is not set, same behavior as before python print(a-b) <xarray.DataArray 'temp' (x: 3, y: 3)> array([[ 0.133102, -1.275794, 1.331784], [ 0.995555, -0.509624, 0.188597], [ 1.922048, -0.053253, -0.293245]]) Dimensions without coordinates: x, y set the option: ```python with xr.set_options(keep_attrs=True): print(a-b)

<xarray.DataArray 'temp' (x: 3, y: 3)> array([[ 0.133102, -1.275794, 1.331784], [ 0.995555, -0.509624, 0.188597], [ 1.922048, -0.053253, -0.293245]]) Dimensions without coordinates: x, y Attributes: units: K ``` works. Hope that helps you.

Thanks for the report! It looks like we definitely overlooked this in arithmetic operations. I agree that keep_attrs=True should mean that attributes are maintained in arithmetic.

Any interest in putting together a PR? - https://github.com/pydata/xarray/pull/2482 has lots of examples of how to implement the option. - https://github.com/pydata/xarray/blob/0d6056e8816e3d367a64f36c7f1a5c4e1ce4ed4e/xarray/core/variable.py#L1665 is where we forget to keep attributes in binary operations.