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gh-161452: Fix python -m random with a non-positive integer input #161453

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gh-161452: Fix python -m random with a non-positive integer input #161453

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5ee6049
gh-161452: Fix python -m random with a non-positive integer input
andresdelfino Nov 5, 2026
7443cc8
Address review: use else block and report a short CLI error
andresdelfino Nov 7, 2026
a4053f7
Update Lib/test/test_random.py
andresdelfino Nov 7, 2026
a61d062
Remove test_main_empty_integer_range
andresdelfino Nov 7, 2026
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12 changes: 9 additions & 3 deletions Lib/random.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1067,15 +1067,17 @@ def main(arg_list: list[str] | None = None) -> int | str:
try:
# Is it an integer?
val = int(val)
return randint(1, val)
except ValueError:
try:
# Is it a float?
val = float(val)
return uniform(0, val)
except ValueError:
# Split in case of space-separated string: "a b c"
return choice(val.split())
else:
return uniform(0, val)
else:
return randint(1, val)

if len(args.input) >= 2:
return choice(args.input)
Expand All @@ -1084,4 +1086,8 @@ def main(arg_list: list[str] | None = None) -> int | str:


if __name__ == '__main__':
print(main())
import sys
try:
print(main())
except ValueError as exc:
sys.exit(f"error: {exc}")
Comment on lines +1089 to +1093

@vstinner vstinner Nov 7, 2026

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You might rename main() to _main() and wrap these lines into a new main() function. So for example, you can call the new main() function in tests instead of having to spawn a new process.

@andresdelfino andresdelfino Nov 7, 2026

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What if I do like gzip instead, and call sys.exit directly from main? So we get the benefit you mention, and follow an existing pattern (personally I always find _main/main confusing).

@vstinner vstinner Nov 7, 2026

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What I suggest is to have a main() function which does everything: parse command line arguments, compute a random value, display the random value, call sys.exit() on error:

if __name__ == '__main__':
    main()

I don't care too much of how main() code would look like :-)

13 changes: 13 additions & 0 deletions Lib/test/test_random.py
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
from collections import abc, Counter

from test.support import warnings_helper
from test.support.script_helper import assert_python_failure


class MyIndex:
Expand Down Expand Up @@ -1482,6 +1483,18 @@ def test_main(self):
random.seed(0)
self.assertEqual(random.main(shlex.split(command)), expected)

def test_empty_integer_range_error(self):
# An integer input is the same as --integer, even when it is
# not positive.
for value in ["0", "-5"]:
for args in [(value,), ("--integer", value)]:
with self.subTest(args=args):
rc, out, err = assert_python_failure("-m", "random", *args)
self.assertEqual(rc, 1)
self.assertEqual(out, b"")
expected = f"error: empty range in randint(1, {value})"
self.assertEqual(err.decode().rstrip(), expected)


if __name__ == "__main__":
unittest.main()
4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-11-05-22-26-44.gh-issue-161452.YfFfjq.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix the :mod:`random` :ref:`command-line interface <random-cli>`
printing a random float for a zero or negative integer input instead of
failing like ``--integer`` does. Both now report a short error message
instead of a traceback.
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