how to query seed used by random.random()?

python random seed
mix picture mix · Feb 16, 2011 · Viewed 33.2k times · Source

Is there any way to find out what seed Python used to seed its random number generator?

I know I can specify my own seed, but I'm quite happy with Python managing it. But, I do want to know what seed it used, so that if I like the results I'm getting in a particular run, I could reproduce that run later. If I had the seed that was used then I could.

If the answer is I can't, then what's the best way to generate a seed myself? I want them to always be different from run to run---I just want to know what was used.

UPDATE: yes, I mean random.random()! mistake... [title updated]

Answer

Zooba picture Zooba · Feb 16, 2011

It is not possible to get the automatic seed back out from the generator. I normally generate seeds like this:

seed = random.randrange(sys.maxsize)
rng = random.Random(seed)
print("Seed was:", seed)

This way it is time-based, so each time you run the script (manually) it will be different, but if you are using multiple generators they won't have the same seed simply because they were created almost simultaneously.

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