Sklearn Pipeline - How to inherit get_params in custom Transformer (not Estimator)

Question

I have a pipeline in scikit-learn that uses a custom transformer I define like below:

class MyPipelineTransformer(TransformerMixin):

which defines functions

__init__, fit() and transform()

However, when I use the pipeline inside RandomizedSearchCV, I get the following error:

'MyPipelineTransformer' object has no attribute 'get_params'

I've read online (e.g. links below)

(Python - sklearn) How to pass parameters to the customize ModelTransformer class by gridsearchcv

http://scikit-learn.org/stable/auto_examples/hetero_feature_union.html

that I could get 'get_params' by inheriting from BaseEstimator, instead of my current code inheriting just from TransformerMixin. But my transformer is not an estimator. Is there any downside to having a non-estimator inherit from BaseEstimator? Or is that the recommended way to get get_params for any transformer (estimator or not) in a pipeline?

I upvoted, and I don't know the answer to your question, but you should name classes using UpperCamelCase. Please, just do it for me. It's driving me nuts. — juanpa.arrivillaga, Aug 23 '16 at 04:41
Thanks, Juanpa. You are correct. Edited accordingly https://www.python.org/dev/peps/pep-0008/#class-names — Max Power, Aug 23 '16 at 04:52
@MaxPower Is your `MyPipelineTransformer` encapsulating several steps in a pipeline? — nanounanue, Jun 19 '17 at 17:33
This question was about a transformer which was a component of a larger sklearn pipeline — Max Power, Jun 19 '17 at 17:36

maxymoo · Accepted Answer · 2017-08-15T22:53:16.350

10

Yes it looks like this is the standard way of achieving this. For example in the source for sklearn.preprocessing we have

class FunctionTransformer(BaseEstimator, TransformerMixin)

edited Aug 15 '17 at 22:53

answered Aug 23 '16 at 05:30

maxymoo

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Note also that `__init__` needs to be set up properly: https://stackoverflow.com/a/68926629/14278409 – njp Nov 12 '22 at 22:36

Sklearn Pipeline - How to inherit get_params in custom Transformer (not Estimator)

1 Answers1