Part of SF patch #1513870 (the still relevant part) -- add reduce() to

functools, and adjust docs etc.

Lib/test/test_functools.py

@@ -259,6 +259,74 @@ class TestWraps(TestUpdateWrapper):
         self.assertEqual(wrapper.attr, 'This is a different test')
         self.assertEqual(wrapper.dict_attr, f.dict_attr)
 
+class TestReduce(unittest.TestCase):
+    func = functools.reduce
+
+    def test_reduce(self):
+        class Squares:
+            def __init__(self, max):
+                self.max = max
+                self.sofar = []
+
+            def __len__(self):
+                return len(self.sofar)
+
+            def __getitem__(self, i):
+                if not 0 <= i < self.max: raise IndexError
+                n = len(self.sofar)
+                while n <= i:
+                    self.sofar.append(n*n)
+                    n += 1
+                return self.sofar[i]
+    
+        self.assertEqual(self.func(lambda x, y: x+y, ['a', 'b', 'c'], ''), 'abc')
+        self.assertEqual(
+            self.func(lambda x, y: x+y, [['a', 'c'], [], ['d', 'w']], []),
+            ['a','c','d','w']
+        )
+        self.assertEqual(self.func(lambda x, y: x*y, range(2,8), 1), 5040)
+        self.assertEqual(
+            self.func(lambda x, y: x*y, range(2,21), 1L),
+            2432902008176640000L
+        )
+        self.assertEqual(self.func(lambda x, y: x+y, Squares(10)), 285)
+        self.assertEqual(self.func(lambda x, y: x+y, Squares(10), 0), 285)
+        self.assertEqual(self.func(lambda x, y: x+y, Squares(0), 0), 0)
+        self.assertRaises(TypeError, self.func)
+        self.assertRaises(TypeError, self.func, 42, 42)
+        self.assertRaises(TypeError, self.func, 42, 42, 42)
+        self.assertEqual(self.func(42, "1"), "1") # func is never called with one item
+        self.assertEqual(self.func(42, "", "1"), "1") # func is never called with one item
+        self.assertRaises(TypeError, self.func, 42, (42, 42))
+
+        class BadSeq:
+            def __getitem__(self, index):
+                raise ValueError
+        self.assertRaises(ValueError, self.func, 42, BadSeq())
+
+    # Test reduce()'s use of iterators.
+    def test_iterator_usage(self):
+        class SequenceClass:
+            def __init__(self, n):
+                self.n = n
+            def __getitem__(self, i):
+                if 0 <= i < self.n:
+                    return i
+                else:
+                    raise IndexError
+    
+        from operator import add
+        self.assertEqual(self.func(add, SequenceClass(5)), 10)
+        self.assertEqual(self.func(add, SequenceClass(5), 42), 52)
+        self.assertRaises(TypeError, self.func, add, SequenceClass(0))
+        self.assertEqual(self.func(add, SequenceClass(0), 42), 42)
+        self.assertEqual(self.func(add, SequenceClass(1)), 0)
+        self.assertEqual(self.func(add, SequenceClass(1), 42), 42)
+
+        d = {"one": 1, "two": 2, "three": 3}
+        self.assertEqual(self.func(add, d), "".join(d.keys()))
+
+    
 
 
 def test_main(verbose=None):
@@ -268,7 +336,8 @@ def test_main(verbose=None):
         TestPartialSubclass,
         TestPythonPartial,
         TestUpdateWrapper,
-        TestWraps
+        TestWraps,
+        TestReduce
     )
     test_support.run_unittest(*test_classes)