UUID values are 128 bits long, guarantee uniqueness across space and time

Used to generate identifiers for documents, hosts, application clients, and other situations where a unique value is necessary

Using IEEE 802 MAC addresses as a source of uniqueness

Using pseudo-random numbers

Using well-known strings combined with cryptographic hashing

generate a UUID for a host, identified by its MAC address

each call to uuid1() returns a new value

import uuid

u = uuid.uuid1()
u.version # version
u.hex # hex
u.int # int
            

Create UUID values from names instead of random or time-based values use cryptographic hash values

The UUID value for a given name in a namespace is always the same, no matter when or where it is calculated

# 'NAMESPACE_DNS','NAMESPACE_OID','NAMESPACE_URL','NAMESPACE_X500',
hostname = 'www.doughellmann.com'

uuid.uuid3(uuid.NAMESPACE_DNS, hostname) # MD5

uuid.uuid5(uuid.NAMESPACE_DNS, hostname) # SHA-1
            

used as a hash key, a more random sequence of values with more differentiation

uuid.uuid4()
            

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