Issue #16148: implemented PEP 424

5 files changed, 60 insertions, 43 deletions

diff --git a/Lib/test/test_enumerate.py b/Lib/test/test_enumerate.py
index 2e904cf..c0560fe 100644
--- a/Lib/test/test_enumerate.py
+++ b/Lib/test/test_enumerate.py
@@ -1,4 +1,5 @@
 import unittest
+import operator
 import sys
 import pickle
 
@@ -168,15 +169,13 @@ class TestReversed(unittest.TestCase, PickleTest):
         x = range(1)
         self.assertEqual(type(reversed(x)), type(iter(x)))
 
-    @support.cpython_only
     def test_len(self):
         # This is an implementation detail, not an interface requirement
-        from test.test_iterlen import len
         for s in ('hello', tuple('hello'), list('hello'), range(5)):
-            self.assertEqual(len(reversed(s)), len(s))
+            self.assertEqual(operator.length_hint(reversed(s)), len(s))
             r = reversed(s)
             list(r)
-            self.assertEqual(len(r), 0)
+            self.assertEqual(operator.length_hint(r), 0)
         class SeqWithWeirdLen:
             called = False
             def __len__(self):
@@ -187,7 +186,7 @@ class TestReversed(unittest.TestCase, PickleTest):
             def __getitem__(self, index):
                 return index
         r = reversed(SeqWithWeirdLen())
-        self.assertRaises(ZeroDivisionError, len, r)
+        self.assertRaises(ZeroDivisionError, operator.length_hint, r)
 
 
     def test_gc(self):
diff --git a/Lib/test/test_iterlen.py b/Lib/test/test_iterlen.py
index 7469a31..57f7101 100644
--- a/Lib/test/test_iterlen.py
+++ b/Lib/test/test_iterlen.py
@@ -45,31 +45,21 @@ import unittest
 from test import support
 from itertools import repeat
 from collections import deque
-from builtins import len as _len
+from operator import length_hint
 
 n = 10
 
-def len(obj):
-    try:
-        return _len(obj)
-    except TypeError:
-        try:
-            # note: this is an internal undocumented API,
-            # don't rely on it in your own programs
-            return obj.__length_hint__()
-        except AttributeError:
-            raise TypeError
 
 class TestInvariantWithoutMutations(unittest.TestCase):
 
     def test_invariant(self):
         it = self.it
         for i in reversed(range(1, n+1)):
-            self.assertEqual(len(it), i)
+            self.assertEqual(length_hint(it), i)
             next(it)
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
         self.assertRaises(StopIteration, next, it)
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
 
 class TestTemporarilyImmutable(TestInvariantWithoutMutations):
 
@@ -78,12 +68,12 @@ class TestTemporarilyImmutable(TestInvariantWithoutMutations):
         # length immutability  during iteration
 
         it = self.it
-        self.assertEqual(len(it), n)
+        self.assertEqual(length_hint(it), n)
         next(it)
-        self.assertEqual(len(it), n-1)
+        self.assertEqual(length_hint(it), n-1)
         self.mutate()
         self.assertRaises(RuntimeError, next, it)
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
 
 ## ------- Concrete Type Tests -------
 
@@ -92,10 +82,6 @@ class TestRepeat(TestInvariantWithoutMutations):
     def setUp(self):
         self.it = repeat(None, n)
 
-    def test_no_len_for_infinite_repeat(self):
-        # The repeat() object can also be infinite
-        self.assertRaises(TypeError, len, repeat(None))
-
 class TestXrange(TestInvariantWithoutMutations):
 
     def setUp(self):
@@ -167,14 +153,15 @@ class TestList(TestInvariantWithoutMutations):
         it = iter(d)
         next(it)
         next(it)
-        self.assertEqual(len(it), n-2)
+        self.assertEqual(length_hint(it), n - 2)
         d.append(n)
-        self.assertEqual(len(it), n-1)  # grow with append
+        self.assertEqual(length_hint(it), n - 1)  # grow with append
         d[1:] = []
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
         self.assertEqual(list(it), [])
         d.extend(range(20))
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
+
 
 class TestListReversed(TestInvariantWithoutMutations):
 
@@ -186,32 +173,41 @@ class TestListReversed(TestInvariantWithoutMutations):
         it = reversed(d)
         next(it)
         next(it)
-        self.assertEqual(len(it), n-2)
+        self.assertEqual(length_hint(it), n - 2)
         d.append(n)
-        self.assertEqual(len(it), n-2)  # ignore append
+        self.assertEqual(length_hint(it), n - 2)  # ignore append
         d[1:] = []
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
         self.assertEqual(list(it), [])  # confirm invariant
         d.extend(range(20))
-        self.assertEqual(len(it), 0)
+        self.assertEqual(length_hint(it), 0)
 
 ## -- Check to make sure exceptions are not suppressed by __length_hint__()
 
 
 class BadLen(object):
-    def __iter__(self): return iter(range(10))
+    def __iter__(self):
+        return iter(range(10))
+
     def __len__(self):
         raise RuntimeError('hello')
 
+
 class BadLengthHint(object):
-    def __iter__(self): return iter(range(10))
+    def __iter__(self):
+        return iter(range(10))
+
     def __length_hint__(self):
         raise RuntimeError('hello')
 
+
 class NoneLengthHint(object):
-    def __iter__(self): return iter(range(10))
+    def __iter__(self):
+        return iter(range(10))
+
     def __length_hint__(self):
-        return None
+        return NotImplemented
+
 
 class TestLengthHintExceptions(unittest.TestCase):
 
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index 90e85a9..ece7f99 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -1723,9 +1723,8 @@ class TestVariousIteratorArgs(unittest.TestCase):
 class LengthTransparency(unittest.TestCase):
 
     def test_repeat(self):
-        from test.test_iterlen import len
-        self.assertEqual(len(repeat(None, 50)), 50)
-        self.assertRaises(TypeError, len, repeat(None))
+        self.assertEqual(operator.length_hint(repeat(None, 50)), 50)
+        self.assertEqual(operator.length_hint(repeat(None), 12), 12)
 
 class RegressionTests(unittest.TestCase):
 
diff --git a/Lib/test/test_operator.py b/Lib/test/test_operator.py
index fa608b9..b445ee0 100644
--- a/Lib/test/test_operator.py
+++ b/Lib/test/test_operator.py
@@ -410,6 +410,31 @@ class OperatorTestCase(unittest.TestCase):
         self.assertEqual(operator.__ixor__     (c, 5), "ixor")
         self.assertEqual(operator.__iconcat__  (c, c), "iadd")
 
+    def test_length_hint(self):
+        class X(object):
+            def __init__(self, value):
+                self.value = value
+
+            def __length_hint__(self):
+                if type(self.value) is type:
+                    raise self.value
+                else:
+                    return self.value
+
+        self.assertEqual(operator.length_hint([], 2), 0)
+        self.assertEqual(operator.length_hint(iter([1, 2, 3])), 3)
+
+        self.assertEqual(operator.length_hint(X(2)), 2)
+        self.assertEqual(operator.length_hint(X(NotImplemented), 4), 4)
+        self.assertEqual(operator.length_hint(X(TypeError), 12), 12)
+        with self.assertRaises(TypeError):
+            operator.length_hint(X("abc"))
+        with self.assertRaises(ValueError):
+            operator.length_hint(X(-2))
+        with self.assertRaises(LookupError):
+            operator.length_hint(X(LookupError))
+
+
 def test_main(verbose=None):
     import sys
     test_classes = (
diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 8e9e587..da62723 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -848,8 +848,6 @@ class TestBasicOps(unittest.TestCase):
         for v in self.set:
             self.assertIn(v, self.values)
         setiter = iter(self.set)
-        # note: __length_hint__ is an internal undocumented API,
-        # don't rely on it in your own programs
         self.assertEqual(setiter.__length_hint__(), len(self.set))
 
     def test_pickling(self):