I'm fairly certain that the netCDF4.Dataset.get_variables_by_attributes behaves as a logical AND.

Here is the currently implementation body from https://github.com/Unidata/netcdf4-python/blob/master/netCDF4/_netCDF4.pyx#L2868 ```python vs = []

has_value_flag = False

this is a hack to make inheritance work in MFDataset

(which stores variables in _vars)

_vars = self.variables if _vars is None: _vars = self._vars for vname in _vars: var = _vars[vname] for k, v in kwargs.items(): if callable(v): has_value_flag = v(getattr(var, k, None)) if has_value_flag is False: break elif hasattr(var, k) and getattr(var, k) == v: has_value_flag = True else: has_value_flag = False break

if has_value_flag is True: vs.append(_vars[vname])

return vs ```

The difference appears to be in the presence of that has_value_flag and the breaks in the innermost loop. I must admit I had a little trouble following the above code, but it seems that when any of they key=value tests fails, it will stop checking the current variable (DataArray in the xarray context) and check the next variable.