Issue 93: Model amount of children

sdv/modeler.py

@@ -35,9 +35,7 @@ class Modeler:
     DEFAULT_PRIMARY_KEY = 'GENERATED_PRIMARY_KEY'
 
     def __init__(self, data_navigator, model=DEFAULT_MODEL, distribution=None, model_kwargs=None):
-        """Instantiates a modeler object.
-
-        """
+        """Instantiates a modeler object."""
         self.tables = {}
         self.models = {}
         self.child_locs = {}  # maps table->{child: col #}
@@ -48,7 +46,7 @@ def __init__(self, data_navigator, model=DEFAULT_MODEL, distribution=None, model
             raise ValueError(
                 '`distribution` argument is only suported for `GaussianMultivariate` model.')
 
-        if distribution:
+        if distribution is not None:
             distribution = get_qualified_name(distribution)
         else:
             distribution = get_qualified_name(DEFAULT_DISTRIBUTION)
@@ -145,16 +143,18 @@ def _flatten_dict(cls, nested, prefix=''):
 
         return result
 
-    def flatten_model(self, model, name=''):
-        """Flatten a model's parameters into an array.
+    def _get_model_dict(self, data):
+        """Fit and  serialize  a model and flatten its parameters into an array.
 
         Args:
-            model(self.model): Instance of model.
-            name (str): Prefix to the parameter name.
+            data(pandas.DataFrame): Dataset to fit the model to.
 
         Returns:
-            pd.Series: parameters for model
+            dict: Flattened parameters for model.
+
         """
+        model = self.fit_model(data)
+
         if self.model == DEFAULT_MODEL:
             values = []
             triangle = np.tril(model.covariance)
@@ -173,7 +173,7 @@ def flatten_model(self, model, name=''):
                     column = pd.DataFrame({'field': [distribution.std]})
                     distribution.std = transformer.reverse_transform(column).loc[0, 'field']
 
-        return pd.Series(self._flatten_dict(model.to_dict(), name))
+        return self._flatten_dict(model.to_dict())
 
     def get_foreign_key(self, fields, primary):
         """Get foreign key from primary key.
@@ -254,16 +254,24 @@ def _create_extension(self, foreign, transformed_child_table, table_info):
 
         foreign_key, child_name = table_info
         try:
-            conditional_data = transformed_child_table.loc[foreign.index].copy()
-            if foreign_key in conditional_data:
-                conditional_data = conditional_data.drop(foreign_key, axis=1)
+            child_rows = transformed_child_table.loc[foreign.index].copy()
+            if foreign_key in child_rows:
+                child_rows = child_rows.drop(foreign_key, axis=1)
 
         except KeyError:
             return None
 
-        if len(conditional_data):
-            clean_df = self.impute_table(conditional_data)
-            return self.flatten_model(self.fit_model(clean_df), child_name)
+        num_child_rows = len(child_rows)
+
+        if num_child_rows:
+            clean_df = self.impute_table(child_rows)
+            extension = self._get_model_dict(clean_df)
+            extension['child_rows'] = num_child_rows
+
+            extension = pd.Series(extension)
+            extension.index = child_name + '__' + extension.index
+
+            return extension
 
         return None