_CustomTransformer.py

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from sklearn.base import TransformerMixin
 
 
class _CustomTransformer(TransformerMixin):
    ''' Data transformer class which validates data shapes. 
        Child classes should override _fit, _transform, _inverse_transform '''
    _input_shape  = None 
    _output_shape = None
 
    def fit(self, X, *args, **kwargs):               
        self._input_shape = X.shape[1]
        self._fit(X.copy(), *args, **kwargs)
        return self 
 
    def transform(self, X, *args, **kwargs):
        self._validate_shape(X, self._input_shape)
        X = self._transform(X.copy(), *args, **kwargs)
        self._validate_shape(X, self._output_shape)
        self._output_shape = X.shape[1]
        return X 
 
    def inverse_transform(self, X, *args, **kwargs):
        self._validate_shape(X, self._output_shape)
        X = self._inverse_transform(X.copy(), *args, **kwargs)
        self._validate_shape(X, self._input_shape)
        self._input_shape = X.shape[1]
        return X 
 
    def fit_transform(self, X, *args, **kwargs):
        self.fit(X, *args, **kwargs)
        return self.transform(X, *args, **kwargs)
 
    @staticmethod
    def config_info(*args, **kwargs):                 return '' # Return any additional info to construct model config
    def _fit(self, X, *args, **kwargs):               pass
    def _transform(self, X, *args, **kwargs):         raise NotImplemented
    def _inverse_transform(self, X, *args, **kwargs): raise NotImplemented
    def _validate_shape(self, X, shape):              assert(shape is None or X.shape[1] == shape), \
        f'Number of data features changed: expected {shape}, found {X.shape[1]}'