FIX: define DataFrame.items for all versions of python (#17214)

Author: tacaswell

Diff for: doc/source/whatsnew/v0.21.0.txt

@@ -128,6 +128,10 @@ Other Enhancements
 - :func:`DataFrame.add_prefix` and :func:`DataFrame.add_suffix` now accept strings containing the '%' character. (:issue:`17151`)
 - `read_*` methods can now infer compression from non-string paths, such as ``pathlib.Path`` objects (:issue:`17206`).
 - :func:`pd.read_sas()` now recognizes much more of the most frequently used date (datetime) formats in SAS7BDAT files (:issue:`15871`).
+- :func:`DataFrame.items` and :func:`Series.items` is now present in both Python 2 and 3 and is lazy in all cases (:issue:`13918`, :issue:`17213`)
+
+
+
 
 .. _whatsnew_0210.api_breaking:
 

Diff for: pandas/core/frame.py

@@ -802,8 +802,7 @@ def itertuples(self, index=True, name="Pandas"):
         # fallback to regular tuples
         return zip(*arrays)
 
-    if compat.PY3:  # pragma: no cover
-        items = iteritems
+    items = iteritems
 
     def __len__(self):
         """Returns length of info axis, but here we use the index """

Diff for: pandas/core/series.py

@@ -1110,8 +1110,7 @@ def iteritems(self):
         """
         return zip(iter(self.index), iter(self))
 
-    if compat.PY3:  # pragma: no cover
-        items = iteritems
+    items = iteritems
 
     # ----------------------------------------------------------------------
     # Misc public methods

Diff for: pandas/tests/frame/test_api.py

@@ -171,7 +171,16 @@ def test_nonzero(self):
     def test_iteritems(self):
         df = self.klass([[1, 2, 3], [4, 5, 6]], columns=['a', 'a', 'b'])
         for k, v in compat.iteritems(df):
-            assert type(v) == self.klass._constructor_sliced
+            assert isinstance(v, self.klass._constructor_sliced)
+
+    def test_items(self):
+        # issue #17213, #13918
+        cols = ['a', 'b', 'c']
+        df = DataFrame([[1, 2, 3], [4, 5, 6]], columns=cols)
+        for c, (k, v) in zip(cols, df.items()):
+            assert c == k
+            assert isinstance(v, Series)
+            assert (df[k] == v).all()
 
     def test_iter(self):
         assert tm.equalContents(list(self.frame), self.frame.columns)

Diff for: pandas/tests/series/test_api.py

@@ -301,6 +301,16 @@ def test_iteritems(self):
         # assert is lazy (genrators don't define reverse, lists do)
         assert not hasattr(self.series.iteritems(), 'reverse')
 
+    def test_items(self):
+        for idx, val in self.series.items():
+            assert val == self.series[idx]
+
+        for idx, val in self.ts.items():
+            assert val == self.ts[idx]
+
+        # assert is lazy (genrators don't define reverse, lists do)
+        assert not hasattr(self.series.items(), 'reverse')
+
     def test_raise_on_info(self):
         s = Series(np.random.randn(10))
         with pytest.raises(AttributeError):