Allow empty tables to be fitted using fit_processed_data (#1526)

* Update preprocess_data

* Fix lint

* Update test

sdv/single_table/base.py

@@ -468,7 +468,9 @@ def fit_processed_data(self, processed_data):
             processed_data (pandas.DataFrame):
                 The transformed data used to fit the model to.
         """
-        self._fit(processed_data)
+        if not processed_data.empty:
+            self._fit(processed_data)
+
         self._fitted = True
         self._fitted_date = datetime.datetime.today().strftime('%Y-%m-%d')
         self._fitted_sdv_version = pkg_resources.get_distribution('sdv').version

tests/unit/multi_table/test_base.py

@@ -718,6 +718,21 @@ def test_fit_processed_data(self):
         instance._model_tables.assert_called_once_with(instance._augment_tables.return_value)
         assert instance._fitted
 
+    def test_fit_processed_data_empty_table(self):
+        """Test attributes are properly set when data is empty and that _fit is not called."""
+        # Setup
+        instance = Mock()
+        data = pd.DataFrame()
+
+        # Run
+        BaseMultiTableSynthesizer.fit_processed_data(instance, data)
+
+        # Assert
+        instance._fit.assert_not_called()
+        assert instance._fitted
+        assert instance._fitted_date
+        assert instance._fitted_sdv_version
+
     def test_fit(self):
         """Test that ``fit`` calls ``preprocess`` and then ``fit_processed_data``."""
         # Setup