Skip to content

Fix _randbelow_with_getrandbits(). #117388

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 2 commits into from
Closed

Fix _randbelow_with_getrandbits(). #117388

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
65d144b
Fix _randbelow_with_getrandbits().
lschoe Mar 30, 2024
695bee6
Fix two failing (deterministically seeded) tests.
lschoe Mar 30, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion Lib/random.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -246,7 +246,7 @@ def _randbelow_with_getrandbits(self, n):
"Return a random int in the range [0,n). Defined for n > 0."

getrandbits = self.getrandbits
k = n.bit_length()
k = (n - 1).bit_length()
r = getrandbits(k) # 0 <= r < 2**k
while r >= n:
r = getrandbits(k)
Expand Down
30 changes: 15 additions & 15 deletions Lib/test/test_generators.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1164,22 +1164,22 @@ def b():
A->F B->B C->C D->D E->F F->F G->G H->H I->I J->J K->B L->L M->M
merged D into C
A->F B->B C->C D->C E->F F->F G->G H->H I->I J->J K->B L->L M->M
merged M into C
A->F B->B C->C D->C E->F F->F G->G H->H I->I J->J K->B L->L M->C
merged J into B
A->F B->B C->C D->C E->F F->F G->G H->H I->I J->B K->B L->L M->C
merged M into B
A->F B->B C->C D->C E->F F->F G->G H->H I->I J->J K->B L->L M->B
merged H into G
A->F B->B C->C D->C E->F F->F G->G H->G I->I J->J K->B L->L M->B
merged B into C
A->F B->C C->C D->C E->F F->F G->G H->H I->I J->C K->C L->L M->C
merged F into G
A->G B->C C->C D->C E->G F->G G->G H->H I->I J->C K->C L->L M->C
merged L into C
A->G B->C C->C D->C E->G F->G G->G H->H I->I J->C K->C L->C M->C
merged G into I
A->I B->C C->C D->C E->I F->I G->I H->H I->I J->C K->C L->C M->C
merged I into H
A->H B->C C->C D->C E->H F->H G->H H->H I->H J->C K->C L->C M->C
merged C into H
A->H B->H C->H D->H E->H F->H G->H H->H I->H J->H K->H L->H M->H
A->F B->C C->C D->C E->F F->F G->G H->G I->I J->J K->C L->L M->C
merged C into G
A->F B->G C->G D->G E->F F->F G->G H->G I->I J->J K->G L->L M->G
merged G into J
A->F B->J C->J D->J E->F F->F G->J H->J I->I J->J K->J L->L M->J
merged J into F
A->F B->F C->F D->F E->F F->F G->F H->F I->I J->F K->F L->L M->F
merged L into F
A->F B->F C->F D->F E->F F->F G->F H->F I->I J->F K->F L->F M->F
merged I into F
A->F B->F C->F D->F E->F F->F G->F H->F I->F J->F K->F L->F M->F

"""
# Emacs turd '
Expand Down
2 changes: 1 addition & 1 deletion Lib/test/test_random.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -800,7 +800,7 @@ def test_randrange_uses_getrandbits(self):
self.gen.seed(1234567)
# If randrange uses getrandbits, it should pick getrandbits(100)
# when called with a 100-bits stop argument.
self.assertEqual(self.gen.randrange(2**99),
self.assertEqual(self.gen.randrange(2**99 + 1),
97904845777343510404718956115)

def test_randbelow_logic(self, _log=log, int=int):
Expand Down