Python generate random: uuid v. md5 v. random which is most efficient or *inefficient*

Question

I want to generate a random short hex string (say 8-digit or 16-digit).

There are tons of options to do this eg, from the top of my head:

uuid.uuid4().hex[:8]
md5().hexdigest()[:8]
"{0:08x}".format(int(random.random()*1000000000))[:8]

What I'm wondering is if there's any reason why any of these methods would be more efficient than any others, or inversely if one would be especially evilly inefficient?

Anyone have any good oil on this?

Any suggestions for the cheapest way of doing this operation in python?

Answer 1

Try them:

> %timeit uuid.uuid4().hex[:8]
100000 loops, best of 3: 7.46 µs per loop

> %timeit "{0:08x}".format(random.randint(0, 0xffffffff))
100000 loops, best of 3: 2.05 µs per loop

> %timeit binascii.hexlify(os.urandom(4))
1000000 loops, best of 3: 1.74 µs per loop

It's notable here that bits from random are not suitable for cryptographic purposes, so while it is likely to be the fastest that may still not be what you want.

If you're looking for crazy efficient, just get a whole bunch of random data beforehand :)

> randomdata = binascii.hexlify(os.urandom(1024))
> %timeit randomdata[64:72]
10000000 loops, best of 3: 101 ns per loop