bpo-38200: Add itertools.pairwise() (GH-23549)
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index 702cf08..df2997e 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -1024,6 +1024,25 @@ def run(r1, r2):
self.assertEqual(next(it), (1, 2))
self.assertRaises(RuntimeError, next, it)
+ def test_pairwise(self):
+ self.assertEqual(list(pairwise('')), [])
+ self.assertEqual(list(pairwise('a')), [])
+ self.assertEqual(list(pairwise('ab')),
+ [('a', 'b')]),
+ self.assertEqual(list(pairwise('abcde')),
+ [('a', 'b'), ('b', 'c'), ('c', 'd'), ('d', 'e')])
+ self.assertEqual(list(pairwise(range(10_000))),
+ list(zip(range(10_000), range(1, 10_000))))
+
+ with self.assertRaises(TypeError):
+ pairwise() # too few arguments
+ with self.assertRaises(TypeError):
+ pairwise('abc', 10) # too many arguments
+ with self.assertRaises(TypeError):
+ pairwise(iterable='abc') # keyword arguments
+ with self.assertRaises(TypeError):
+ pairwise(None) # non-iterable argument
+
def test_product(self):
for args, result in [
([], [()]), # zero iterables
@@ -1787,6 +1806,10 @@ def test_islice(self):
a = []
self.makecycle(islice([a]*2, None), a)
+ def test_pairwise(self):
+ a = []
+ self.makecycle(pairwise([a]*5), a)
+
def test_permutations(self):
a = []
self.makecycle(permutations([1,2,a,3], 3), a)
@@ -1995,6 +2018,17 @@ def test_islice(self):
self.assertRaises(TypeError, islice, N(s), 10)
self.assertRaises(ZeroDivisionError, list, islice(E(s), 10))
+ def test_pairwise(self):
+ for s in ("123", "", range(1000), ('do', 1.2), range(2000,2200,5)):
+ for g in (G, I, Ig, S, L, R):
+ seq = list(g(s))
+ expected = list(zip(seq, seq[1:]))
+ actual = list(pairwise(g(s)))
+ self.assertEqual(actual, expected)
+ self.assertRaises(TypeError, pairwise, X(s))
+ self.assertRaises(TypeError, pairwise, N(s))
+ self.assertRaises(ZeroDivisionError, list, pairwise(E(s)))
+
def test_starmap(self):
for s in (range(10), range(0), range(100), (7,11), range(20,50,5)):
for g in (G, I, Ig, S, L, R):
@@ -2312,15 +2346,6 @@ def test_permutations_sizeof(self):
... else:
... return starmap(func, repeat(args, times))
->>> def pairwise(iterable):
-... "s -> (s0,s1), (s1,s2), (s2, s3), ..."
-... a, b = tee(iterable)
-... try:
-... next(b)
-... except StopIteration:
-... pass
-... return zip(a, b)
-
>>> def grouper(n, iterable, fillvalue=None):
... "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
... args = [iter(iterable)] * n
@@ -2451,15 +2476,6 @@ def test_permutations_sizeof(self):
>>> take(5, map(int, repeatfunc(random.random)))
[0, 0, 0, 0, 0]
->>> list(pairwise('abcd'))
-[('a', 'b'), ('b', 'c'), ('c', 'd')]
-
->>> list(pairwise([]))
-[]
-
->>> list(pairwise('a'))
-[]
-
>>> list(islice(pad_none('abc'), 0, 6))
['a', 'b', 'c', None, None, None]