Github user ajaysaini725 commented on a diff in the pull request:
https://github.com/apache/spark/pull/18746#discussion_r130775517
--- Diff: python/pyspark/ml/base.py ---
@@ -116,3 +121,44 @@ class Model(Transformer):
"""
__metaclass__ = ABCMeta
+
+
+@inherit_doc
+class UnaryTransformer(HasInputCol, HasOutputCol, Transformer):
+
+ @abstractmethod
+ def createTransformFunc(self):
+ """
+ Creates the transoform function using the given param map.
+ """
+ raise NotImplementedError()
+
+ @abstractmethod
+ def outputDataType(self):
+ """
+ Returns the data type of the output column as a sql type
+ """
+ raise NotImplementedError()
+
+ @abstractmethod
+ def validateInputType(self, inputType):
+ """
+ Validates the input type. Throws an exception if it is invalid.
+ """
+ raise NotImplementedError()
+
+ def transformSchema(self, schema):
+ inputType = schema[self.getInputCol()].dataType
+ self.validateInputType(inputType)
+ if self.getOutputCol() in schema.names:
+ raise ValueError("Output column %s already exists." %
self.getOutputCol())
+ outputFields = copy.copy(schema.fields)
+ outputFields.append(StructField(self.getOutputCol(),
+ self.outputDataType(),
+ nullable=False))
+ return StructType(outputFields)
+
+ def transform(self, dataset, paramMap=None):
+ transformSchema(dataset.schema())
+ transformUDF = udf(self.createTransformFunc(),
self.outputDataType())
+ dataset.withColumn(self.getOutputCol(),
transformUDF(self.getInputCol()))
--- End diff --
self.createTransformFunc returns a function which is passed to the udf so
in this case I think it is okay
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