[issue40346] Redesign random.Random class inheritance

[STINNER Victor]

STINNER Victor <vstinner at python.org> added the comment:

Example with Python 3.8:
---
import random

class MyRandom(random.Random):
    def getrandbits(self, n):
        return 0

my = MyRandom()
print([my.randint(1, 6) for _ in range(3)])
print([my.random() for _ in range(3)])
---

Output:
---
[1, 1, 1]
[0.5654641798814677, 0.610057019404943, 0.7526620665660224]
---

[1, 1, 1] is what I expect, but what are these random [0.5654641798814677, 0.610057019404943, 0.7526620665660224] numbers?

This behavior is surprising me. I would expect the base class to be "empty", not to inherit Mersenne Twister. If I don't implement all required abstract methods: I would either expect an error when the class is created, or at least when the method is called.


Raymond:
> Am not sure I'm comfortable with you defining random() in pure python dividing by BPF -- that seems like a C level decision.

My PR 19631 doesn't change random.Random.random() (still implemented in C) nor random.SystemRandom.random() (same Python implementation): they should produce exactly the same random floating point numbers.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40346>
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