API: catch target kwarg clobbering

Author: TomAugspurger

pandas/core/generic.py

@@ -2089,6 +2089,9 @@ def sample(self, n=None, frac=None, replace=False, weights=None, random_state=No
     def pipe(self, func, *args, **kwargs):
         if isinstance(func, tuple):
             func, target = func
+            if target in kwargs:
+                msg = '%s is both the pipe target and a keyword argument' % target
+                raise ValueError(msg)
             kwargs[target] = self
             return func(*args, **kwargs)
         else:

pandas/tests/test_generic.py

@@ -1668,6 +1668,15 @@ def test_pipe_tuple(self):
         result = df.A.pipe((f, 'y'), 0)
         self.assert_series_equal(result, df.A)
 
+    def test_pipe_tuple_error(self):
+        df = DataFrame({"A": [1, 2, 3]})
+        f = lambda x, y: y
+        with tm.assertRaises(ValueError):
+            result = df.pipe((f, 'y'), x=1, y=0)
+
+        with tm.assertRaises(ValueError):
+            result = df.A.pipe((f, 'y'), x=1, y=0)
+
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],
                    exit=False)