Support multi-column transformers (#692)

* def + store_columns

* hypertransformer modif 1

* unit test

* docstring

* drop _store_columns change

* add integration_test + _get_output_to_property

* ordered_columns + prefix

* 'int' in integration test

* change prefix + columns_to_sdtype

* docstring

* columns_to_sdtypes

* validate column_to_sdtype ValueError + docstring

* fix _get_prefix

* move PR, hypertransformer with multi column

* break line

rdt/hyper_transformer.py

@@ -14,6 +14,7 @@
 from rdt.transformers import (
     BaseTransformer, get_class_by_transformer_name, get_default_transformer,
     get_transformers_by_type)
+from rdt.transformers.utils import flatten_column_list
 
 LOGGER = logging.getLogger(__name__)
 
@@ -25,7 +26,7 @@ def __repr__(self):
         """Pretty print the dictionary."""
         config = {
             'sdtypes': self['sdtypes'],
-            'transformers': {k: repr(v) for k, v in self['transformers'].items()}
+            'transformers': {str(k): repr(v) for k, v in self['transformers'].items()}
         }
 
         printed = json.dumps(config, indent=4)
@@ -115,7 +116,7 @@ def __init__(self):
         self._specified_fields = set()
         self._validate_field_transformers()
         self._valid_output_sdtypes = self._DEFAULT_OUTPUT_SDTYPES
-        self._multi_column_fields = self._create_multi_column_fields()
+        self._multi_column_fields = {}
         self._transformers_sequence = []
         self._output_columns = []
         self._input_columns = []
@@ -205,7 +206,18 @@ def _validate_config(config):
 
         sdtypes = config['sdtypes']
         transformers = config['transformers']
-        if set(sdtypes.keys()) != set(transformers.keys()):
+
+        sdtype_keys = sdtypes.keys()
+        transformer_keys = flatten_column_list(transformers.keys())
+
+        is_transformer_keys_unique = len(transformer_keys) == len(set(transformer_keys))
+        if not is_transformer_keys_unique:
+            raise InvalidConfigError(
+                'Error: Invalid config. Please provide unique keys for the sdtypes '
+                'and transformers.'
+            )
+
+        if set(sdtype_keys) != set(transformer_keys):
             raise InvalidConfigError(
                 "The column names in the 'sdtypes' dictionary must match the "
                 "column names in the 'transformers' dictionary."
@@ -216,10 +228,14 @@ def _validate_config(config):
 
         mismatched_columns = []
         for column_name, transformer in transformers.items():
-            if transformer is not None:
-                sdtype = sdtypes.get(column_name)
+            if transformer is None:
+                continue
+
+            columns = column_name if isinstance(column_name, tuple) else [column_name]
+            for column in columns:
+                sdtype = sdtypes.get(column)
                 if sdtype not in transformer.get_supported_sdtypes():
-                    mismatched_columns.append(column_name)
+                    mismatched_columns.append(column)
 
         if mismatched_columns:
             raise InvalidConfigError(
@@ -519,6 +535,19 @@ def detect_initial_config(self, data):
         LOGGER.info('Config:')
         LOGGER.info(str(config))
 
+    def _get_columns_to_sdtypes(self, field):
+        """Generate the ``columns_to_sdtypes`` dict for the given field.
+
+        Args:
+            field (tuple):
+                Names of the column for the multi column trnasformer.
+        """
+        columns_to_sdtypes = {}
+        for column in field:
+            columns_to_sdtypes[column] = self.field_sdtypes[column]
+
+        return columns_to_sdtypes
+
     def _fit_field_transformer(self, data, field, transformer):
         """Fit a transformer to its corresponding field.
 
@@ -541,7 +570,12 @@ def _fit_field_transformer(self, data, field, transformer):
             self._output_columns.append(field)
 
         else:
-            transformer.fit(data, field)
+            if isinstance(field, tuple):
+                columns_to_sdtypes = self._get_columns_to_sdtypes(field)
+                transformer.fit(data, columns_to_sdtypes)
+            else:
+                transformer.fit(data, field)
+
             self._transformers_sequence.append(transformer)
             data = transformer.transform(data)
 
@@ -609,8 +643,8 @@ def fit(self, data):
         self._validate_detect_config_called(data)
         self._unfit()
         self._input_columns = list(data.columns)
-        for field in self._input_columns:
-            data = self._fit_field_transformer(data, field, self.field_transformers[field])
+        for field_column, field_transformer in self.field_transformers.items():
+            data = self._fit_field_transformer(data, field_column, field_transformer)
 
         self._validate_all_fields_fitted()
         self._fitted = True

rdt/transformers/__init__.py

@@ -9,7 +9,7 @@
 from functools import lru_cache
 from pathlib import Path
 
-from rdt.transformers.base import BaseTransformer
+from rdt.transformers.base import BaseMultiColumnTransformer, BaseTransformer
 from rdt.transformers.boolean import BinaryEncoder
 from rdt.transformers.categorical import (
     CustomLabelEncoder, FrequencyEncoder, LabelEncoder, OneHotEncoder, OrderedLabelEncoder,
@@ -22,6 +22,7 @@
 
 __all__ = [
     'BaseTransformer',
+    'BaseMultiColumnTransformer',
     'BinaryEncoder',
     'ClusterBasedNormalizer',
     'CustomLabelEncoder',

rdt/transformers/base.py

@@ -362,7 +362,7 @@ def _fit(self, columns_data):
         raise NotImplementedError()
 
     def _set_seed(self, data):
-        hash_value = self.get_input_column()
+        hash_value = self.columns[0]
         for value in data.head(5):
             hash_value += str(value)
 
@@ -479,3 +479,113 @@ def reverse_transform(self, data):
         data = self._add_columns_to_data(data, reversed_data, self.columns)
 
         return data
+
+
+class BaseMultiColumnTransformer(BaseTransformer):
+    """Base class for all multi column transformers.
+
+    The ``BaseMultiColumnTransformer`` class contains methods that must be implemented
+    in order to create a new multi column transformer.
+
+    Attributes:
+        columns_to_sdtypes (dict):
+            Dictionary mapping each column to its sdtype.
+    """
+
+    def __init__(self):
+        super().__init__()
+        self.columns_to_sdtypes = {}
+
+    def get_input_column(self):
+        """Override ``get_input_column`` method from ``BaseTransformer``.
+
+        Raise an error because for multi column transformers, ``get_input_columns``
+        must be used instead.
+        """
+        raise NotImplementedError(
+            'MultiColumnTransformers does not have a single input column.'
+            'Please use ``get_input_columns`` instead.'
+        )
+
+    def get_input_columns(self):
+        """Return input column name for transformer.
+
+        Returns:
+            list:
+                Input column names.
+        """
+        return self.columns
+
+    def _get_prefix(self):
+        """Return the prefix of the output columns.
+
+        Returns:
+            str:
+                Prefix of the output columns.
+        """
+        raise NotImplementedError()
+
+    def _get_output_to_property(self, property_):
+        self.column_prefix = self._get_prefix()
+        output = {}
+        for output_column, properties in self.output_properties.items():
+            # if 'sdtype' is not in the dict, ignore the column
+            if property_ not in properties:
+                continue
+
+            if self.column_prefix is None:
+                output[f'{output_column}'] = properties[property_]
+            else:
+                output[f'{self.column_prefix}.{output_column}'] = properties[property_]
+
+        return output
+
+    def _validate_columns_to_sdtypes(self, data, columns_to_sdtypes):
+        """Check that all the columns in ``columns_to_sdtypes`` are present in the data."""
+        missing = set(columns_to_sdtypes.keys()) - set(data.columns)
+        if missing:
+            missing_to_print = ', '.join(missing)
+            raise ValueError(f'Columns ({missing_to_print}) are not present in the data.')
+
+    def _fit(self, data):
+        """Fit the transformer to the data.
+
+        Args:
+            data (pandas.DataFrame):
+                Data to transform.
+        """
+        raise NotImplementedError()
+
+    @random_state
+    def fit(self, data, columns_to_sdtypes):
+        """Fit the transformer to a ``column`` of the ``data``.
+
+        Args:
+            data (pandas.DataFrame):
+                The entire table.
+            columns_to_sdtypes (dict):
+                Dictionary mapping each column to its sdtype.
+        """
+        self._validate_columns_to_sdtypes(data, columns_to_sdtypes)
+        self.columns_to_sdtypes = columns_to_sdtypes
+        self._store_columns(list(self.columns_to_sdtypes.keys()), data)
+        self._set_seed(data)
+        columns_data = self._get_columns_data(data, self.columns)
+        self._fit(columns_data)
+        self._build_output_columns(data)
+
+    def fit_transform(self, data, columns_to_sdtypes):
+        """Fit the transformer to a `column` of the `data` and then transform it.
+
+        Args:
+            data (pandas.DataFrame):
+                The entire table.
+            columns_to_sdtypes (dict):
+                Dictionary mapping each column to its sdtype.
+
+        Returns:
+            pd.DataFrame:
+                The entire table, containing the transformed data.
+        """
+        self.fit(data, columns_to_sdtypes)
+        return self.transform(data)

rdt/transformers/utils.py

@@ -163,3 +163,24 @@ def fill_nan_with_none(data):
             Original data with nan values replaced by None.
     """
     return data.fillna(np.nan).replace([np.nan], [None])
+
+
+def flatten_column_list(column_list):
+    """Flatten a list of columns.
+
+    Args:
+        column_list (list):
+            List of columns to flatten.
+
+    Returns:
+        list:
+            Flattened list of columns.
+    """
+    flattened = []
+    for column in column_list:
+        if isinstance(column, tuple):
+            flattened.extend(column)
+        else:
+            flattened.append(column)
+
+    return flattened

tests/integration/test_hyper_transformer.py

@@ -6,12 +6,14 @@
 import pandas as pd
 import pytest
 
-from rdt import HyperTransformer, get_demo
+from rdt import get_demo
 from rdt.errors import ConfigNotSetError, InvalidConfigError, InvalidDataError, NotFittedError
+from rdt.hyper_transformer import Config, HyperTransformer
 from rdt.transformers import (
-    AnonymizedFaker, BaseTransformer, BinaryEncoder, ClusterBasedNormalizer, FloatFormatter,
-    FrequencyEncoder, LabelEncoder, OneHotEncoder, RegexGenerator, UniformEncoder,
-    UnixTimestampEncoder, get_default_transformer, get_default_transformers)
+    AnonymizedFaker, BaseMultiColumnTransformer, BaseTransformer, BinaryEncoder,
+    ClusterBasedNormalizer, FloatFormatter, FrequencyEncoder, LabelEncoder, OneHotEncoder,
+    RegexGenerator, UniformEncoder, UnixTimestampEncoder, get_default_transformer,
+    get_default_transformers)
 from rdt.transformers.datetime import OptimizedTimestampEncoder
 from rdt.transformers.numerical import GaussianNormalizer
 from rdt.transformers.pii.anonymizer import PseudoAnonymizedFaker
@@ -55,6 +57,29 @@ def _reverse_transform(self, data):
 TEST_DATA_INDEX = [4, 6, 3, 8, 'a', 1.0, 2.0, 3.0]
 
 
+class DummyMultiColumnTransformerNumerical(BaseMultiColumnTransformer):
+    """Multi column transformer that takes categorical data."""
+
+    SUPPORTED_SDTYPES = ['categorical', 'boolean']
+
+    def _fit(self, data):
+        self.output_properties = {
+            column: {
+                'sdtype': 'numerical',
+                'next_transformer': None,
+            } for column in self.columns
+        }
+
+    def _get_prefix(self):
+        return None
+
+    def _transform(self, data):
+        return data.astype(float)
+
+    def _reverse_transform(self, data):
+        return data.astype(str)
+
+
 def get_input_data():
     datetimes = pd.to_datetime([
         '2010-02-01',
@@ -1418,3 +1443,40 @@ def test_random_seed(self):
 
         # Assert
         pd.testing.assert_frame_equal(reversed1, reversed2)
+
+    def test_hypertransformer_with_mutli_column_transformer_end_to_end(self):
+        """Test ``HyperTransformer`` with mutli column transformers end to end."""
+        # Setup
+        data_test = pd.DataFrame({
+            'A': ['1.0', '2.0', '3.0'],
+            'B': ['4.0', '5.0', '6.0'],
+            'C': [True, False, True]
+        })
+        dict_config = {
+            'sdtypes': {
+                'A': 'categorical',
+                'B': 'categorical',
+                'C': 'boolean'
+            },
+            'transformers': {
+                ('A', 'B'): DummyMultiColumnTransformerNumerical(),
+                'C': UniformEncoder()
+            }
+        }
+        config = Config(dict_config)
+        ht = HyperTransformer()
+        ht.set_config(config)
+
+        # Run
+        transformed_data = ht.fit_transform(data_test)
+        reverse_transformed_data = ht.reverse_transform(transformed_data)
+
+        # Assert
+        expected_transformed_data = pd.DataFrame({
+            'A': [1.0, 2.0, 3.0],
+            'B': [4.0, 5.0, 6.0],
+            'C': [0.5892351646057272, 0.8615278122985615, 0.36493646501970534]
+        })
+
+        pd.testing.assert_frame_equal(transformed_data, expected_transformed_data)
+        pd.testing.assert_frame_equal(reverse_transformed_data, data_test)

tests/integration/test_transformers.py

@@ -69,7 +69,7 @@ def _is_valid_transformer(transformer_name):
     """Determine if transformer should be tested or not."""
     invalid_names = [
         'IdentityTransformer', 'Dummy', 'OrderedLabelEncoder', 'CustomLabelEncoder',
-        'OrderedUniformEncoder',
+        'OrderedUniformEncoder', 'BaseMultiColumnTransformer'
     ]
     return all(invalid_name not in transformer_name for invalid_name in invalid_names)