Python 3.8:

>>> import random
>>> r = random.Random(False)
>>> r
<random.Random object at 0x5611716e8b00>

Python 3.9 alpha 4:

>>> import random
>>> r = random.Random(False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python3.9/random.py", line 100, in __init__
    self.seed(x)
  File "/usr/lib64/python3.9/random.py", line 163, in seed
    super().seed(a)
TypeError: descriptor '__abs__' of 'int' object needs an argument

This arose in the context of Fedora builds with python 3.9.  The networkx project reversed two arguments, resulting in False being passed to random.Random instead of the intended seed value.  I'm glad we noticed the problem with 3.9 so the intended value will now be used, but that TypeError message doesn't really indicate the nature of the problem.  Could you arrange for a better message?

Possibly related to https://bugs.python.org/issue32554 https://github.com/python/cpython/pull/15382 Deprecate hashing arbitrary types in random.seed()

The lines here look odd to me: https://github.com/python/cpython/blob/363fab83b8a0e6d924c7a7c577feec6a2812bb8c/Modules/_randommodule.c#L290-L291

    args[0] = arg;
    n = PyObject_Vectorcall(_randomstate_global->Long___abs__, args, 0,
                                         NULL);

Should that 0 in the PyObject_Vectorcall be a 1 instead?

> Should that 0 in the PyObject_Vectorcall be a 1 instead?

Right. I proposed PR 18897 to fix it and add an unit test on seed(False).

Fixed by:

New changeset 00d7cd8ab8db2c1e1f591ade828f88a1a973d70f by Victor Stinner in branch 'master':
bpo-38075: Fix random_seed(): use PyObject_CallOneArg() (GH-18897)
https://github.com/python/cpython/commit/00d7cd8ab8db2c1e1f591ade828f88a1a973d70f