Efficiently generate a 16-character, alphanumeric

问题:

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?

回答1:

As none of the answers provide you with a random string consisting of characters 0-9, a-z, A-Z: Here is a working solution which will give you approx. 4.5231285e+74 keys:

import random, string
x = ''.join(random.choice(string.ascii_uppercase + string.ascii_lowercase + string.digits) for _ in range(16))
print(x)

It is also very readable without knowing ASCII codes by heart.

There is an even shorter version since python 3.6.2:

import random, string
x = ''.join(random.choices(string.ascii_letters + string.digits, k=16))
print(x)

回答2:

You can use this:

>>> import random
>>> ''.join(random.choice('0123456789ABCDEF') for i in range(16))
'E2C6B2E19E4A7777'

There is no guarantee that the keys generated will be unique so you should be ready to retry with a new key in the case the original insert fails. Also, you might want to consider using a deterministic algorithm to generate a string from an auto-incremented id instead of using random values, as this will guarantee you uniqueness (but it will also give predictable keys).

回答3:

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.

回答4:

For random numbers a good source is os.urandom:

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

回答5:

>>> import random
>>> ''.join(random.sample(map(chr, range(48, 57) + range(65, 90) + range(97, 122)), 16))
'CDh0geq3NpKtcXfP'

回答6:

This value is incremented by 1 on each call (it wraps around). Deciding where the best place to store the value will depend on how you are using it. You may find this explanation of interest, as it discusses not only how Guids work but also how to make a smaller one.

The short answer is this: Use some of those characters as a timestamp and the other characters as a "uniquifier," a value increments by 1 on each call to your uid generator.

回答7:

simply use python inbuilt uuid :

import uuid
print uuid.uuid4().hex[:16].upper()

回答8:

Simply use python builtin uuid:

If UUIDs are okay for your purposes use the built in uuid package.

One Line Solution:

>>> import uuid
>>> str(uuid.uuid4().get_hex().upper()[0:16])
'40003A9B8C3045CA'