ENH: add get_level_values method and tests, address GH #188

Author: wesm

RELEASE.rst

@@ -22,6 +22,7 @@ This is an incremental bug fix and performance enhancement release
     substantial speed increases
   - Added `is_monotonic` property to `Index` classes with associated Cython
     code to evaluate the monotonicity of the `Index` values
+  - Add method `get_level_values` to `MultiIndex`
 
 **Improvements to existing features**
 
@@ -35,6 +36,9 @@ This is an incremental bug fix and performance enhancement release
     created. Substantial performance increases result (GH #176)
   - Substantially improved performance of generic `Index.intersection` and
     `Index.union`
+  - Improved performance of `DateRange.union` with overlapping ranges and
+    non-cacheable offsets (like Minute). Implemented analogous fast
+    `DateRange.intersection` for overlapping ranges.
   - Implemented `BlockManager.take` resulting in significantly faster `take`
     performance on mixed-type `DataFrame` objects (GH #104)
   - Improved performance of `Series.sort_index`
@@ -56,6 +60,12 @@ This is an incremental bug fix and performance enhancement release
   - Finish implementation of as_index=False in groupby for DataFrame
     aggregation (GH #181)
 
+Thanks
+------
+
+- Uri Laserson
+- Scott Sinclair
+
 pandas 0.4.1
 ============
 

pandas/core/index.py

@@ -779,6 +779,23 @@ def values(self):
         result[:] = list(self)
         return result
 
+    def get_level_values(self, level):
+        """
+        Return vector of label values for requested level, equal to the length
+        of the index
+
+        Parameters
+        ----------
+        level : int
+
+        Returns
+        -------
+        values : ndarray
+        """
+        unique_vals = self.levels[level].values
+        labels = self.labels[level]
+        return unique_vals.take(labels)
+
     def __contains__(self, key):
         try:
             label_key = self._get_label_key(key)

pandas/tests/test_index.py

@@ -335,6 +335,11 @@ def test_from_arrays(self):
         result = MultiIndex.from_arrays(arrays)
         self.assertEquals(list(result), list(self.index))
 
+    def test_get_level_values(self):
+        result = self.index.get_level_values(0)
+        expected = ['foo', 'foo', 'bar', 'baz', 'qux', 'qux']
+        self.assert_(np.array_equal(result, expected))
+
     def test_nlevels(self):
         self.assertEquals(self.index.nlevels, 2)