Generalize filter(f, seq) to work with iterators. This also generalizes
filter() to no longer insist that len(seq) be defined.
NEEDS DOC CHANGES.
diff --git a/Lib/test/test_iter.py b/Lib/test/test_iter.py
index 5b9bf65..952ab66 100644
--- a/Lib/test/test_iter.py
+++ b/Lib/test/test_iter.py
@@ -275,4 +275,48 @@
except OSError:
pass
+ # Test filter()'s use of iterators.
+ def test_builtin_filter(self):
+ self.assertEqual(filter(None, SequenceClass(5)), range(1, 5))
+ self.assertEqual(filter(None, SequenceClass(0)), [])
+ self.assertEqual(filter(None, ()), ())
+ self.assertEqual(filter(None, "abc"), "abc")
+
+ d = {"one": 1, "two": 2, "three": 3}
+ self.assertEqual(filter(None, d), d.keys())
+
+ self.assertRaises(TypeError, filter, None, list)
+ self.assertRaises(TypeError, filter, None, 42)
+
+ class Boolean:
+ def __init__(self, truth):
+ self.truth = truth
+ def __nonzero__(self):
+ return self.truth
+ True = Boolean(1)
+ False = Boolean(0)
+
+ class Seq:
+ def __init__(self, *args):
+ self.vals = args
+ def __iter__(self):
+ class SeqIter:
+ def __init__(self, vals):
+ self.vals = vals
+ self.i = 0
+ def __iter__(self):
+ return self
+ def next(self):
+ i = self.i
+ self.i = i + 1
+ if i < len(self.vals):
+ return self.vals[i]
+ else:
+ raise StopIteration
+ return SeqIter(self.vals)
+
+ seq = Seq(*([True, False] * 25))
+ self.assertEqual(filter(lambda x: not x, seq), [False]*25)
+ self.assertEqual(filter(lambda x: not x, iter(seq)), [False]*25)
+
run_unittest(TestCase)