Hex digest for Python's built-in hash function

Question

I need to create an identifier token from a set of nested configuration values. The token can be part of a URL, so – to make processing easier – it should contain only hexadecimal digits (or something similar). The config values are nested tuples with elements of hashable types like int, bool, str etc.

My idea was to use the built-in hash() function, as this will continue to work even if the config structure changes. This is my first attempt:

def token(config):
    h = hash(config)
    return '{:X}'.format(h)

This will produce tokens of variable length, but that doesn't matter. What bothers me, though, is that the token might contain a leading minus sign, since the return value of hash() is a signed integer.

As a way to avoid the sign, I thought of the following work-around, which is adding a constant to the hash value. This constant should be half the size of the range the value of hash() can take (which is platform-dependent, eg. different for 32-/64-bit systems):

HALF_HASH_RANGE = 2**(sys.hash_info.width-1)

Is this a sane and portable solution? Or will I shoot myself in the foot with this?

I also saw suggestions for using struct.pack() (which returns a bytes object, on which one can call the .hex() method), but it also requires knowing the range of the hash value in advance (for the choice of the right format character).

Addendum:
Encryption strength or collisions by chance are not an issue. The drawback of the hashlib library in this scenario is that it requires writing a converter that traverses the input structure and converts everything into a bytes representation, which is cumbersome.

Answer 1

You can use any of hash functions for getting unique string. Right now python support out of the box many algorithms, like: md5, sha1, sha224, sha256, sha384, sha512. You can read more about it here - https://docs.python.org/2/library/hashlib.html

This example shows how to use library hashlib. (Python 3)

>>> import hashlib
>>> sha = hashlib.sha256()
>>> sha.update('somestring'.encode())
>>> sha.hexdigest()
>>> '63f6fe797026d794e0dc3e2bd279aee19dd2f8db67488172a644bb68792a570c'

Also you can try library hashids. But note that it's not a hash algorithm and you (and anyone who knows salt) can decrypt data.

$ pip install hashids

Basic usage:

>>> from hashids import Hashids
>>> hashids = Hashids()
>>> hashids.encode(123)
'Mj3'
>>> hashids.decode('Mj3')
123