[andresdelfino]

When python -m random gets a single integer input, main() called randint() inside the try block that converts the input with int(). For an integer N <= 0, the ValueError that randint() raises for an empty range was taken to mean that the input is not an integer, so python -m random 0 printed 0.0 and a negative N printed a random negative float. This keeps only the conversions inside the try blocks (the randint() and uniform() calls move to else: blocks), so an integer input now behaves like --integer N, as documented.

Run from the command line, both forms now print a one-line error and exit with status 1, instead of a traceback:

$ ./python -m random -3
error: empty range in randint(1, -3)
$ ./python -m random --integer 0
error: empty range in randint(1, 0)

main() itself still raises the ValueError; only the __main__ block catches it.

The new tests check that 0 and -5 raise the same ValueError from main() with and without --integer, and that the command line reports the short error message.

🤖 Generated with Claude Code

• Issue: python -m random N prints a float for an integer N <= 0 #161452

[gvanrossum]

Don't you want to move this to an (inner) else: block too?

[skirpichev]

FWIW, I think it's the right place: uniform() not raises (c.f. randint).

So, here we have only parsing failures for floats. In that case it's reasonable to try choice() as a fallback.

[andresdelfino]

While Sergey is right, it would be easier to read if the same pattern is followed. Let's to think of. Let me know what you prefer.

[vstinner]

I agree with @gvanrossum, it's better to move return uniform(0, val) to an else: block as well.

[andresdelfino]

Applied

[vstinner]

This change is backward incompatible, but it respects the documentation: https://docs.python.org/dev/library/random.html#command-line-usage

If no options are given, the output depends on the input:
Integer: same as --integer.

Hum. Displaying a long traceback is not really user friendly. Can you catch the exception and display a (short) error message instead?

$ ./python -m random -3
Traceback (most recent call last):
  File "/home/vstinner/python/main/Lib/runpy.py", line 201, in _run_module_as_main
    return _run_code(code, main_globals, None,
                     "__main__", mod_spec)
  File "/home/vstinner/python/main/Lib/runpy.py", line 87, in _run_code
    exec(code, run_globals)
    ~~~~^^^^^^^^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/random.py", line 1088, in <module>
    print(main())
          ~~~~^^
  File "/home/vstinner/python/main/Lib/random.py", line 1079, in main
    return randint(1, val)
  File "/home/vstinner/python/main/Lib/random.py", line 341, in randint
    raise ValueError(f"empty range in randint({a}, {b})")
ValueError: empty range in randint(1, -3)

cc @hugovk who authored this feature.

[hugovk]

Yes, a short error message would be better than the traceback.

[andresdelfino]

@vstinner I applied your suggestion, handling the exception in the block that calls main. Changing the main function itself would involve more changes in the tests. Would it be better to go that way?

[vstinner]

Some general notes on random CLI. I'm not sure that it's worth it to change them. I just wanted to share my findings.

---

./python -m random single_choice always returns single_choice. I suppose that it's a deliberate behavior. It's similar to ./python -m random 1 which returns always 1 and ./python -m random --float 0 which returns always 0.0.

---

There is a surprising behavior when the integer is larger than sys.get_int_max_str_digits(). int() raises ValueError: Exceeds the limit (4300 digits) for integer string conversion: value has 40096 digits and so switchs to float() which returns inf:

$ ./python -m random $(python -c "print('1'*40096)")
inf

$ ./python -m random $(python -c "print('-' + '1'*40096)")
-inf

$ ./python -m random --integer $(python -c "print('1'*40096)")
usage: python -m random [-h] [-c CHOICE [CHOICE ...] | -i N | -f N] [input ...]
python -m random: error: argument -i/--integer: invalid int value: '111111111111(...)111'

$ ./python -m random --integer $(python -c "print('-' + '1'*40096)")
usage: python -m random [-h] [-c CHOICE [CHOICE ...] | -i N | -f N] [input ...]
python -m random: error: argument -i/--integer: invalid int value: '-1111111111111(...)111'

---

By the way, it's possible to pass special float values:

$ ./python -m random --float inf
inf

$ ./python -m random --float nan
nan

It seems like random.uniform() always return inf when the maximum is inf:

$ ./python
>>> random.uniform(0, float('inf'))
inf

Ok, maybe it can return nan if self.random() returns 0.0 which is unlikely but possible :-)

And random.uniform(0, float('nan')) always return nan.

stale

[vstinner]

LGTM. I just have a last suggestion about adding a "real" random.main() function.

[vstinner]

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.