Add support for MaskedArray in Series constructor, with test

pandas/core/series.py

@@ -11,6 +11,7 @@
 
 from numpy import nan, ndarray
 import numpy as np
+import numpy.ma as ma
 
 from pandas.core.common import (isnull, notnull, _is_bool_indexer,
                                 _default_index, _maybe_upcast,
@@ -2045,6 +2046,11 @@ def remove_na(arr):
 
 def _sanitize_array(data, index, dtype=None, copy=False,
                     raise_cast_failure=False):
+    if isinstance(data, ma.MaskedArray):
+        mask = ma.getmaskarray(data)
+        data = ma.copy(data)
+        data[mask] = np.nan
+
     try:
         subarr = np.array(data, dtype=dtype, copy=copy)
     except (ValueError, TypeError):

pandas/tests/test_series.py

@@ -10,6 +10,7 @@
 
 from numpy import nan
 import numpy as np
+import numpy.ma as ma
 
 from pandas import Index, Series, TimeSeries, DataFrame, isnull, notnull
 from pandas.core.index import MultiIndex
@@ -189,6 +190,19 @@ def test_constructor(self):
         self.assertRaises(Exception, Series, np.random.randn(3, 3),
                           index=np.arange(3))
 
+    def test_constructor_maskedarray(self):
+        data = ma.masked_all((3,), dtype=float)
+        result = Series(data)
+        expected = Series([nan, nan, nan])
+        assert_series_equal(result, expected)
+        
+        data[0] = 0.0
+        data[2] = 2.0
+        index = ['a', 'b', 'c']
+        result = Series(data, index=index)
+        expected = Series([0.0, nan, 2.0], index=index)
+        assert_series_equal(result, expected)
+
     def test_constructor_default_index(self):
         s = Series([0, 1, 2])
         assert_almost_equal(s.index, np.arange(3))