bpo-33203: Ensure random.choice always raises IndexError on empty seq… · python/cpython@e25af93 (original) (raw)

3 files changed

lines changed

Original file line number	Diff line number	Diff line change
@@ -241,6 +241,8 @@ def _randbelow(self, n, int=int, maxsize=1<<BPF, type=type,
241	241	"enough bits to choose from a population range this large.\n"
242	242	"To remove the range limitation, add a getrandbits() method.")
243	243	return int(random() * n)
	244	+if n == 0:
	245	+raise ValueError("Boundary cannot be zero")
244	246	rem = maxsize % n
245	247	limit = (maxsize - rem) / maxsize # int(limit * maxsize) % n == 0
246	248	r = random()

Original file line number	Diff line number	Diff line change
@@ -644,7 +644,10 @@ def test_randbelow_overridden_random(self, random_mock):
644	644	# Population range too large (n >= maxsize)
645	645	self.gen._randbelow(maxsize+1, maxsize = maxsize)
646	646	self.gen._randbelow(5640, maxsize = maxsize)
647		-
	647	+# issue 33203: test that _randbelow raises ValueError on
	648	+# n == 0 also in its getrandbits-independent branch.
	649	+with self.assertRaises(ValueError):
	650	+self.gen._randbelow(0, maxsize=maxsize)
648	651	# This might be going too far to test a single line, but because of our
649	652	# noble aim of achieving 100% test coverage we need to write a case in
650	653	# which the following line in Random._randbelow() gets executed:

Original file line number	Diff line number	Diff line change
@@ -0,0 +1,3 @@
	1	+``random.Random.choice()`` now raises ``IndexError`` for empty sequences
	2	+consistently even when called from subclasses without a ``getrandbits()``
	3	+implementation.