Add IntegerArray.size, fix pandas-dev#25580.

Signed-off-by: HE, Tao <[email protected]>

Author: sighingnow

pandas/core/arrays/integer.py

@@ -400,6 +400,10 @@ def __setitem__(self, key, value):
     def __len__(self):
         return len(self._data)
 
+    @property
+    def size(self):
+        return self._data.size
+
     @property
     def nbytes(self):
         return self._data.nbytes + self._mask.nbytes

pandas/tests/resample/test_datetime_index.py

@@ -101,6 +101,18 @@ def test_resample_basic(series, closed, expected):
     assert_series_equal(result, expected)
 
 
+def test_resample_integerarray():
+    # resample on IntegerArray
+    ts = pd.Series(range(9),
+                   index=pd.date_range('1/1/2000', periods=9, freq='T'),
+                   dtype='Int64')
+    result = ts.resample('3T').sum()
+    expected = Series([3, 12, 21],
+                      index=pd.date_range('1/1/2000', periods=3, freq='3T'),
+                      dtype="Int64")
+    assert_series_equal(result, expected)
+
+
 def test_resample_basic_grouper(series):
     s = series
     result = s.resample('5Min').last()