Efficiently generate a 16-character, alphanumeric

Question

I'm looking for a very quick way to generate an alphanumeric unique id for a primary key in a table.

Would something like this work?

def genKey():
    hash = hashlib.md5(RANDOM_NUMBER).digest().encode("base64")
    alnum_hash = re.sub(r'[^a-zA-Z0-9]', "", hash)
    return alnum_hash[:16]

What would be a good way to generate random numbers? If I base it on microtime, I have to account for the possibility of several calls of genKey() at the same time from different instances.

Or is there a better way to do all this?

Answer 1

Have a look at the uuid module (Python 2.5+).

A quick example:

>>> import uuid
>>> uid = uuid.uuid4()
>>> uid.hex
'df008b2e24f947b1b873c94d8a3f2201'

Note that the OP asked for a 16-character alphanumeric string, but UUID4 strings are 32 characters long. You should not truncate this string, instead, use the complete 32 characters.

Answer 2

For random numbers a good source is os.urandom:

 >> import os
 >> import hashlib
 >> random_data = os.urandom(128)
 >> hashlib.md5(random_data).hexdigest()[:16]