DEP: Deprecate np.sum(generator)

Fixes #10652

Introduced in a13aad3ac33b629f3e696b4d4d5dbf4b5605d567

2 files changed, 12 insertions, 0 deletions

diff --git a/numpy/core/fromnumeric.py b/numpy/core/fromnumeric.py
index de85c1143..6c7ef4c1f 100644
--- a/numpy/core/fromnumeric.py
+++ b/numpy/core/fromnumeric.py
@@ -1881,6 +1881,12 @@ def sum(a, axis=None, dtype=None, out=None, keepdims=np._NoValue):
     if keepdims is not np._NoValue:
         kwargs['keepdims'] = keepdims
     if isinstance(a, _gentype):
+        # 2018-02-25, 1.15.0
+        warnings.warn(
+            "Calling np.sum(generator) is deprecated, and in the future will give a different result. "
+            "Use np.sum(np.from_iter(generator)) or the python sum builtin instead.",
+            DeprecationWarning, stacklevel=2)
+
         res = _sum_(a)
         if out is not None:
             out[...] = res
diff --git a/numpy/core/tests/test_deprecations.py b/numpy/core/tests/test_deprecations.py
index fe0c7cc5f..5e6f14a39 100644
--- a/numpy/core/tests/test_deprecations.py
+++ b/numpy/core/tests/test_deprecations.py
@@ -481,5 +481,11 @@ class TestBincount(_DeprecationTestCase):
         self.assert_deprecated(lambda: np.bincount([1, 2, 3], minlength=None))
 
 
+class TestGeneratorSum(_DeprecationTestCase):
+    # 2018-02-25, 1.15.0
+    def test_generator_sum(self):
+        self.assert_deprecated(np.sum, args=((i for i in range(5)),))
+
+
 if __name__ == "__main__":
     run_module_suite()