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Add lambda filter for earthkit.data.Field objects (#16)
* add earthkit.data.Field lambda filter and tests
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| # (C) Copyright 2024 Anemoi contributors. | ||
| # | ||
| # This software is licensed under the terms of the Apache Licence Version 2.0 | ||
| # which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. | ||
| # | ||
| # In applying this licence, ECMWF does not waive the privileges and immunities | ||
| # granted to it by virtue of its status as an intergovernmental organisation | ||
| # nor does it submit to any jurisdiction. | ||
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| import typing as tp | ||
| import importlib | ||
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| from anemoi.transform.filters.base import SimpleFilter | ||
| from anemoi.transform.filters import filter_registry | ||
| from earthkit.data.core.fieldlist import Field, FieldList | ||
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| @filter_registry.register("earthkitfieldlambda") | ||
| class EarthkitFieldLambdaFilter(SimpleFilter): | ||
| """A filter to apply an arbitrary function to individual fields.""" | ||
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| def __init__( | ||
| self, | ||
| fn: str | tp.Callable[[Field, tp.Any], Field], | ||
| param: str | list[str], | ||
| args: list = [], | ||
| kwargs: dict[str, tp.Any] = {}, | ||
| backward_fn: str | tp.Callable[[Field, tp.Any], Field] | None = None, | ||
| ): | ||
| """Initialise the EarthkitFieldLambdaFilter. | ||
| Parameters | ||
| ---------- | ||
| fn: callable or str | ||
| The lambda function as a callable with the general signature | ||
| `fn(*earthkit.data.Field, *args, **kwargs) -> earthkit.data.Field` or | ||
| a string path to the function, such as "package.module.function". | ||
| param: list or str | ||
| The parameter name or list of parameter names to apply the function to. | ||
| args: list | ||
| The list of arguments to pass to the lambda function. | ||
| kwargs: dict | ||
| The dictionary of keyword arguments to pass to the lambda function. | ||
| backward_fn (optional): callable, str or None | ||
| The backward lambda function as a callable with the general signature | ||
| `backward_fn(*earthkit.data.Field, *args, **kwargs) -> earthkit.data.Field` or | ||
| a string path to the function, such as "package.module.function". | ||
| Examples | ||
| -------- | ||
| >>> from anemoi.transform.filters.lambda_filters import EarthkitFieldLambdaFilter | ||
| >>> import earthkit.data as ekd | ||
| >>> fields = ekd.from_source( | ||
| ... "mars",{"param": ["2t"], | ||
| ... "levtype": "sfc", | ||
| ... "dates": ["2023-11-17 00:00:00"]}) | ||
| >>> kelvin_to_celsius = EarthkitFieldLambdaFilter( | ||
| ... fn=lambda x, s: x.clone(values=x.values - s), | ||
| ... param="2t", | ||
| ... args=[273.15], | ||
| ... ) | ||
| >>> fields = kelvin_to_celsius.forward(fields) | ||
| """ | ||
| if not isinstance(args, list): | ||
| raise ValueError("Expected 'args' to be a list. " | ||
| f"Got {args} instead.") | ||
| if not isinstance(kwargs, dict): | ||
| raise ValueError("Expected 'kwargs' to be a dictionary. " | ||
| f"Got {kwargs} instead.") | ||
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| self.fn = self._import_fn(fn) if isinstance(fn, str) else fn | ||
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| if isinstance(backward_fn, str): | ||
| self.backward_fn = self._import_fn(backward_fn) | ||
| else: | ||
| self.backward_fn = backward_fn | ||
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| self.param = param if isinstance(param, list) else [param] | ||
| self.args = args | ||
| self.kwargs = kwargs | ||
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| def forward(self, data: FieldList) -> FieldList: | ||
| return self._transform(data, self.forward_transform, *self.param) | ||
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| def backward(self, data: FieldList) -> FieldList: | ||
| if self.backward_fn: | ||
| return self._transform(data, self.backward_transform, *self.param) | ||
| raise NotImplementedError(f"{self} is not reversible.") | ||
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| def forward_transform(self, *fields: Field) -> tp.Iterator[Field]: | ||
| """Apply the lambda function to the field.""" | ||
| yield self.fn(*fields, *self.args, **self.kwargs) | ||
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| def backward_transform(self, *fields: Field) -> tp.Iterator[Field]: | ||
| """Apply the backward lambda function to the field.""" | ||
| yield self.backward_fn(*fields, *self.args, **self.kwargs) | ||
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| def _import_fn(self, fn: str) -> tp.Callable[..., Field]: | ||
| try: | ||
| module_name, fn_name = fn.rsplit(".", 1) | ||
| module = importlib.import_module(module_name) | ||
| return getattr(module, fn_name) | ||
| except Exception as e: | ||
| raise ValueError(f"Could not import function {fn}") from e | ||
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| def __repr__(self): | ||
| out = f"{self.__class__.__name__}(fn={self.fn}," | ||
| if self.backward_fn: | ||
| out += f"backward_fn={self.backward_fn}," | ||
| out += f"param={self.param}," | ||
| out += f"args={self.args}," | ||
| out += f"kwargs={self.kwargs}," | ||
| out += ")" | ||
| return out |
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