Function merge_attrs

xarray/structure/merge.py:636–685

Combine attributes from different variables according to combine_attrs

(variable_attrs, combine_attrs, context=None)

def merge_attrs(variable_attrs, combine_attrs, context=None):
    """Combine attributes from different variables according to combine_attrs"""
    if not variable_attrs:
        # no attributes to merge
        return None

    if callable(combine_attrs):
        return combine_attrs(variable_attrs, context=context)
    elif combine_attrs == "drop":
        return {}
    elif combine_attrs == "override":
        return dict(variable_attrs[0])
    elif combine_attrs == "no_conflicts":
        result = dict(variable_attrs[0])
        for attrs in variable_attrs[1:]:
            try:
                result = compat_dict_union(result, attrs)
            except ValueError as e:
                raise MergeError(
                    "combine_attrs='no_conflicts', but some values are not "
                    f"the same. Merging {result} with {attrs}"
                ) from e
        return result
    elif combine_attrs == "drop_conflicts":
        result = {}
        dropped_keys = set()

        for attrs in variable_attrs:
            for key, value in attrs.items():
                if key in dropped_keys:
                    continue

                if key not in result:
                    result[key] = value
                elif not equivalent_attrs(result[key], value):
                    del result[key]
                    dropped_keys.add(key)

        return result
    elif combine_attrs == "identical":
        result = dict(variable_attrs[0])
        for attrs in variable_attrs[1:]:
            if not dict_equiv(result, attrs):
                raise MergeError(
                    f"combine_attrs='identical', but attrs differ. First is {result} "
                    f", other is {attrs}."
                )
        return result
    else:
        raise ValueError(f"Unrecognised value for combine_attrs={combine_attrs}")


class _MergeResult(NamedTuple):