Enhance apply_filter_query to be a no-op if no filters are supplied.

urbansim/models/hedonic.py

@@ -3,25 +3,29 @@
 import statsmodels.formula.api as smf
 
 
-def apply_filter_query(df, filters):
+def apply_filter_query(df, filters=None):
     """
     Use the DataFrame.query method to filter a table down to the
     desired rows.
 
     Parameters
     ----------
     df : pandas.DataFrame
-    filters : list of str
+    filters : list of str, optional
         List of filters to apply. Will be joined together with
         ' and ' and passed to DataFrame.query.
+        If not supplied no filtering will be done.
 
     Returns
     -------
     filtered_df : pandas.DataFrame
 
     """
-    query = ' and '.join(filters)
-    return df.query(query)
+    if filters:
+        query = ' and '.join(filters)
+        return df.query(query)
+    else:
+        return df
 
 
 def fit_model(df, filters, model_expression):

urbansim/models/tests/test_hedonic.py

@@ -40,4 +40,12 @@ def test_apply_filter_query_or(test_df):
     pdt.assert_frame_equal(filtered, expected)
 
 
+def test_apply_filter_query_no_filter(test_df):
+    filters = []
+    filtered = hedonic.apply_filter_query(test_df, filters)
+    expected = test_df
+    pdt.assert_frame_equal(filtered, expected)
+
 
+# def test_fit_model(test_df):
+#     filters = []