Add __next__(), next() to ResultProxyreview/mike_bayer/ticket_4077

Added ``__next__()`` and ``next()`` methods to :class:`.ResultProxy`,
so that the ``next()`` builtin function works on the object directly.
:class:`.ResultProxy` has long had an ``__iter__()`` method which already
allows it to respond to the ``iter()`` builtin.   The implementation
for ``__iter__()`` is unchanged, as performance testing has indicated
that iteration using a ``__next__()`` method with ``StopIteration``
is about 20% slower in both Python 2.7 and 3.6.

Change-Id: I70569a4c48ad85a3c21a7ad422f270a559926cfb
Fixes: #4077

3 files changed, 44 insertions, 0 deletions

diff --git a/doc/build/changelog/unreleased_12/4077.rst b/doc/build/changelog/unreleased_12/4077.rst
new file mode 100644
index 000000000..b051d47ba
--- /dev/null
+++ b/doc/build/changelog/unreleased_12/4077.rst
@@ -0,0 +1,11 @@
+.. change::
+    :tags: feature, engine
+    :tickets: 4077
+
+    Added ``__next__()`` and ``next()`` methods to :class:`.ResultProxy`,
+    so that the ``next()`` builtin function works on the object directly.
+    :class:`.ResultProxy` has long had an ``__iter__()`` method which already
+    allows it to respond to the ``iter()`` builtin.   The implementation
+    for ``__iter__()`` is unchanged, as performance testing has indicated
+    that iteration using a ``__next__()`` method with ``StopIteration``
+    is about 20% slower in both Python 2.7 and 3.6.
\ No newline at end of file
diff --git a/lib/sqlalchemy/engine/result.py b/lib/sqlalchemy/engine/result.py
index 3aae932f2..79f362500 100644
--- a/lib/sqlalchemy/engine/result.py
+++ b/lib/sqlalchemy/engine/result.py
@@ -862,6 +862,8 @@ class ResultProxy(object):
             self.closed = True
 
     def __iter__(self):
+        """Implement iteration protocol."""
+
         while True:
             row = self.fetchone()
             if row is None:
@@ -869,6 +871,20 @@ class ResultProxy(object):
             else:
                 yield row
 
+    def __next__(self):
+        """Implement the next() protocol.
+
+        .. versionadded:: 1.2
+
+        """
+        row = self.fetchone()
+        if row is None:
+            raise StopIteration()
+        else:
+            return row
+
+    next = __next__
+
     @util.memoized_property
     def inserted_primary_key(self):
         """Return the primary key for the row just inserted.
diff --git a/test/sql/test_resultset.py b/test/sql/test_resultset.py
index 41092efe9..5c7108ca0 100644
--- a/test/sql/test_resultset.py
+++ b/test/sql/test_resultset.py
@@ -61,6 +61,23 @@ class ResultProxyTest(fixtures.TablesTest):
             rows.append(row)
         eq_(len(rows), 3)
 
+    def test_row_next(self):
+        users = self.tables.users
+
+        users.insert().execute(
+            {'user_id': 7, 'user_name': 'jack'},
+            {'user_id': 8, 'user_name': 'ed'},
+            {'user_id': 9, 'user_name': 'fred'},
+        )
+        r = users.select().execute()
+        rows = []
+        while True:
+            row = next(r, 'foo')
+            if row == 'foo':
+                break
+            rows.append(row)
+        eq_(len(rows), 3)
+
     @testing.requires.subqueries
     def test_anonymous_rows(self):
         users = self.tables.users