Source code for spooq2.transformer.transformer

"""
Transformers take a :py:class:`pyspark.sql.DataFrame` as an input, transform it accordingly 
and return a PySpark DataFrame.   

Each Transformer class has to have a `transform` method which takes no arguments 
and returns a PySpark DataFrame.

Possible transformation methods can be **Selecting the most up to date record by id**,
**Exploding an array**, **Filter (on an exploded array)**, **Apply basic threshold cleansing** or 
**Map the incoming DataFrame to at provided structure**.
"""

from builtins import object
import logging


class Transformer(object):
    """
    Base Class of Transformer Classes.

    Attributes
    ----------
    name : :any:`str`
        Sets the `__name__` of the class' type as `name`, which is essentially the Class' Name.
    logger : :any:`logging.Logger`
        Shared, class level logger for all instances.
    """

    def __init__(self):
        self.name = type(self).__name__
        self.logger = logging.getLogger("spooq2")

    def transform(self, input_df):
        """
        Performs a transformation on a DataFrame.

        Parameters
        ----------
        input_df : :py:class:`pyspark.sql.DataFrame`
            Input DataFrame

        Returns
        -------
        :py:class:`pyspark.sql.DataFrame`
            Transformed DataFrame.

        Note
        ----
        This method does only take the Input DataFrame as a parameters. All other needed parameters
        are defined in the initialization of the Transformator Object.
        """
        raise NotImplementedError("This method has to be implemented in the subclasses")

    def __str__(self):
        return "Transformer Object of Class {nm}".format(nm=self.name)