FIX be robust to obscure callables that are false.

amueller · amueller · commit 73532be1fd8d · 2015-08-03T11:48:21.000-04:00
diff --git a/sklearn/preprocessing/function_transformer.py b/sklearn/preprocessing/function_transformer.py
@@ -61,4 +61,5 @@ def transform(self, X, y=None):
         if self.validate:
             X = check_array(X, self.accept_sparse)
 
-        return (self.func or _identity)(X, *((y,) if self.pass_y else ()))
+        return (self.func is not None or _identity)(
+            X, *((y,) if self.pass_y else ()))
