How to generate unique 64 bits integers from Python?

Question

I need to generate unique 64 bits integers from Python. I\'ve checked out the UUID module. But the UUID it generates are 128 bits integers. So that wouldn\'t work.

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Answer 1

You can use uuid4() which generates a single random 128-bit integer UUID. We have to 'binary right shift' (>>) each 128-bit integer generated by 64-bit (i.e. 128 - (128 - 64)).

from uuid import uuid4

bit_size = 64
sized_unique_id = uuid4().int >> bit_size
print(sized_unique_id)

Answer 2

64 bits unique

What's wrong with counting? A simple counter will create unique values. This is the simplest and it's easy to be sure you won't repeat a value.

Or, if counting isn't good enough, try this.

>>> import random
>>> random.getrandbits(64)
5316191164430650570L

Depending on how you seed and use your random number generator, that should be unique.

You can -- of course -- do this incorrectly and get a repeating sequence of random numbers. Great care must be taken with how you handle seeds for a program that starts and stops.

Answer 3

A 64-bit random number from the OS's random number generator rather than a PRNG:

>>> from struct import unpack; from os import urandom
>>> unpack("!Q", urandom(8))[0]
12494068718269657783L

Answer 4

just mask the 128bit int

>>> import uuid
>>> uuid.uuid4().int & (1<<64)-1
9518405196747027403L
>>> uuid.uuid4().int & (1<<64)-1
12558137269921983654L

These are more or less random, so you have a tiny chance of a collision

Perhaps the first 64 bits of uuid1 is safer to use

>>> uuid.uuid1().int>>64
9392468011745350111L
>>> uuid.uuid1().int>>64
9407757923520418271L
>>> uuid.uuid1().int>>64
9418928317413528031L

These are largely based on the clock, so much less random but the uniqueness is better