Add __getitem__ and __getattr__ to _DataFrameWrapper.

They return a Series, either from the wrapped frame or
from an added computed column.

urbansim/sim/simulation.py

@@ -45,6 +45,14 @@ def columns(self):
         """
         return self._frame.columns + _list_columns_for_table(self.name)
 
+    @property
+    def index(self):
+        """
+        Table index.
+
+        """
+        return self._frame.index
+
     def to_frame(self, columns=None):
         """
         Make a DataFrame with the given columns.
@@ -92,6 +100,27 @@ def update_col(self, column_name, series):
     def __setitem__(self, key, value):
         return self.update_col(key, value)
 
+    def get_column(self, column_name):
+        """
+        Returns a column as a Series.
+
+        Parameters
+        ----------
+        column_name : str
+
+        Returns
+        -------
+        column : pandas.Series
+
+        """
+        return self.to_frame(columns=[column_name])[column_name]
+
+    def __getitem__(self, key):
+        return self.get_column(key)
+
+    def __getattr__(self, key):
+        return self.get_column(key)
+
 
 class _TableFuncWrapper(object):
     """

urbansim/sim/tests/test_simulation.py

@@ -32,6 +32,12 @@ def test_func(test_frame):
 
     assert set(sim.list_tables()) == {'test_frame', 'test_func'}
 
+    table = sim.get_table('test_frame')
+    pdt.assert_index_equal(table.index, df.index)
+    pdt.assert_series_equal(table.get_column('a'), df.a)
+    pdt.assert_series_equal(table.a, df.a)
+    pdt.assert_series_equal(table['b'], df['b'])
+
     table = sim.get_table('test_func')
 
     pdt.assert_frame_equal(table.to_frame(), df / 2)