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cpython/Lib/uuid.py

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r"""UUID objects (universally unique identifiers) according to RFC 4122.
This module provides immutable UUID objects (class UUID) and the functions
uuid1(), uuid3(), uuid4(), uuid5() for generating version 1, 3, 4, and 5
UUIDs as specified in RFC 4122.
If all you want is a unique ID, you should probably call uuid1() or uuid4().
Note that uuid1() may compromise privacy since it creates a UUID containing
the computer's network address. uuid4() creates a random UUID.
Typical usage:
>>> import uuid
# make a UUID based on the host ID and current time
>>> uuid.uuid1() # doctest: +SKIP
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')
# make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')
# make a random UUID
>>> uuid.uuid4() # doctest: +SKIP
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')
# make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')
# make a UUID from a string of hex digits (braces and hyphens ignored)
>>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')
# convert a UUID to a string of hex digits in standard form
>>> str(x)
'00010203-0405-0607-0809-0a0b0c0d0e0f'
# get the raw 16 bytes of the UUID
>>> x.bytes
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'
# make a UUID from a 16-byte string
>>> uuid.UUID(bytes=x.bytes)
UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')
"""
import os
import sys
from enum import Enum, _simple_enum
__author__ = 'Ka-Ping Yee <ping@zesty.ca>'
# The recognized platforms - known behaviors
if sys.platform in ('win32', 'darwin'):
_AIX = _LINUX = False
else:
import platform
_platform_system = platform.system()
_AIX = _platform_system == 'AIX'
_LINUX = _platform_system == 'Linux'
_MAC_DELIM = b':'
_MAC_OMITS_LEADING_ZEROES = False
if _AIX:
_MAC_DELIM = b'.'
_MAC_OMITS_LEADING_ZEROES = True
RESERVED_NCS, RFC_4122, RESERVED_MICROSOFT, RESERVED_FUTURE = [
'reserved for NCS compatibility', 'specified in RFC 4122',
'reserved for Microsoft compatibility', 'reserved for future definition']
int_ = int # The built-in int type
bytes_ = bytes # The built-in bytes type
@_simple_enum(Enum)
class SafeUUID:
safe = 0
unsafe = -1
unknown = None
class UUID:
"""Instances of the UUID class represent UUIDs as specified in RFC 4122.
UUID objects are immutable, hashable, and usable as dictionary keys.
Converting a UUID to a string with str() yields something in the form
'12345678-1234-1234-1234-123456789abc'. The UUID constructor accepts
five possible forms: a similar string of hexadecimal digits, or a tuple
of six integer fields (with 32-bit, 16-bit, 16-bit, 8-bit, 8-bit, and
48-bit values respectively) as an argument named 'fields', or a string
of 16 bytes (with all the integer fields in big-endian order) as an
argument named 'bytes', or a string of 16 bytes (with the first three
fields in little-endian order) as an argument named 'bytes_le', or a
single 128-bit integer as an argument named 'int'.
UUIDs have these read-only attributes:
bytes the UUID as a 16-byte string (containing the six
integer fields in big-endian byte order)
bytes_le the UUID as a 16-byte string (with time_low, time_mid,
and time_hi_version in little-endian byte order)
fields a tuple of the six integer fields of the UUID,
which are also available as six individual attributes
and two derived attributes:
time_low the first 32 bits of the UUID
time_mid the next 16 bits of the UUID
time_hi_version the next 16 bits of the UUID
clock_seq_hi_variant the next 8 bits of the UUID
clock_seq_low the next 8 bits of the UUID
node the last 48 bits of the UUID
time the 60-bit timestamp
clock_seq the 14-bit sequence number
hex the UUID as a 32-character hexadecimal string
int the UUID as a 128-bit integer
urn the UUID as a URN as specified in RFC 4122
variant the UUID variant (one of the constants RESERVED_NCS,
RFC_4122, RESERVED_MICROSOFT, or RESERVED_FUTURE)
version the UUID version number (1 through 5, meaningful only
when the variant is RFC_4122)
is_safe An enum indicating whether the UUID has been generated in
a way that is safe for multiprocessing applications, via
uuid_generate_time_safe(3).
"""
__slots__ = ('int', 'is_safe', '__weakref__')
def __init__(self, hex=None, bytes=None, bytes_le=None, fields=None,
int=None, version=None,
*, is_safe=SafeUUID.unknown):
r"""Create a UUID from either a string of 32 hexadecimal digits,
a string of 16 bytes as the 'bytes' argument, a string of 16 bytes
in little-endian order as the 'bytes_le' argument, a tuple of six
integers (32-bit time_low, 16-bit time_mid, 16-bit time_hi_version,
8-bit clock_seq_hi_variant, 8-bit clock_seq_low, 48-bit node) as
the 'fields' argument, or a single 128-bit integer as the 'int'
argument. When a string of hex digits is given, curly braces,
hyphens, and a URN prefix are all optional. For example, these
expressions all yield the same UUID:
UUID('{12345678-1234-5678-1234-567812345678}')
UUID('12345678123456781234567812345678')
UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
UUID(bytes='\x12\x34\x56\x78'*4)
UUID(bytes_le='\x78\x56\x34\x12\x34\x12\x78\x56' +
'\x12\x34\x56\x78\x12\x34\x56\x78')
UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
UUID(int=0x12345678123456781234567812345678)
Exactly one of 'hex', 'bytes', 'bytes_le', 'fields', or 'int' must
be given. The 'version' argument is optional; if given, the resulting
UUID will have its variant and version set according to RFC 4122,
overriding the given 'hex', 'bytes', 'bytes_le', 'fields', or 'int'.
is_safe is an enum exposed as an attribute on the instance. It
indicates whether the UUID has been generated in a way that is safe
for multiprocessing applications, via uuid_generate_time_safe(3).
"""
if [hex, bytes, bytes_le, fields, int].count(None) != 4:
raise TypeError('one of the hex, bytes, bytes_le, fields, '
'or int arguments must be given')
if hex is not None:
hex = hex.replace('urn:', '').replace('uuid:', '')
hex = hex.strip('{}').replace('-', '')
if len(hex) != 32:
raise ValueError('badly formed hexadecimal UUID string')
int = int_(hex, 16)
if bytes_le is not None:
if len(bytes_le) != 16:
raise ValueError('bytes_le is not a 16-char string')
bytes = (bytes_le[4-1::-1] + bytes_le[6-1:4-1:-1] +
bytes_le[8-1:6-1:-1] + bytes_le[8:])
if bytes is not None:
if len(bytes) != 16:
raise ValueError('bytes is not a 16-char string')
assert isinstance(bytes, bytes_), repr(bytes)
int = int_.from_bytes(bytes) # big endian
if fields is not None:
if len(fields) != 6:
raise ValueError('fields is not a 6-tuple')
(time_low, time_mid, time_hi_version,
clock_seq_hi_variant, clock_seq_low, node) = fields
if not 0 <= time_low < 1<<32:
raise ValueError('field 1 out of range (need a 32-bit value)')
if not 0 <= time_mid < 1<<16:
raise ValueError('field 2 out of range (need a 16-bit value)')
if not 0 <= time_hi_version < 1<<16:
raise ValueError('field 3 out of range (need a 16-bit value)')
if not 0 <= clock_seq_hi_variant < 1<<8:
raise ValueError('field 4 out of range (need an 8-bit value)')
if not 0 <= clock_seq_low < 1<<8:
raise ValueError('field 5 out of range (need an 8-bit value)')
if not 0 <= node < 1<<48:
raise ValueError('field 6 out of range (need a 48-bit value)')
clock_seq = (clock_seq_hi_variant << 8) | clock_seq_low
int = ((time_low << 96) | (time_mid << 80) |
(time_hi_version << 64) | (clock_seq << 48) | node)
if int is not None:
if not 0 <= int < 1<<128:
raise ValueError('int is out of range (need a 128-bit value)')
if version is not None:
if not 1 <= version <= 5:
raise ValueError('illegal version number')
# Set the variant to RFC 4122.
int &= ~(0xc000 << 48)
int |= 0x8000 << 48
# Set the version number.
int &= ~(0xf000 << 64)
int |= version << 76
object.__setattr__(self, 'int', int)
object.__setattr__(self, 'is_safe', is_safe)
def __getstate__(self):
d = {'int': self.int}
if self.is_safe != SafeUUID.unknown:
# is_safe is a SafeUUID instance. Return just its value, so that
# it can be un-pickled in older Python versions without SafeUUID.
d['is_safe'] = self.is_safe.value
return d
def __setstate__(self, state):
object.__setattr__(self, 'int', state['int'])
# is_safe was added in 3.7; it is also omitted when it is "unknown"
object.__setattr__(self, 'is_safe',
SafeUUID(state['is_safe'])
if 'is_safe' in state else SafeUUID.unknown)
def __eq__(self, other):
if isinstance(other, UUID):
return self.int == other.int
return NotImplemented
# Q. What's the value of being able to sort UUIDs?
# A. Use them as keys in a B-Tree or similar mapping.
def __lt__(self, other):
if isinstance(other, UUID):
return self.int < other.int
return NotImplemented
def __gt__(self, other):
if isinstance(other, UUID):
return self.int > other.int
return NotImplemented
def __le__(self, other):
if isinstance(other, UUID):
return self.int <= other.int
return NotImplemented
def __ge__(self, other):
if isinstance(other, UUID):
return self.int >= other.int
return NotImplemented
def __hash__(self):
return hash(self.int)
def __int__(self):
return self.int
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__, str(self))
def __setattr__(self, name, value):
raise TypeError('UUID objects are immutable')
def __str__(self):
hex = '%032x' % self.int
return '%s-%s-%s-%s-%s' % (
hex[:8], hex[8:12], hex[12:16], hex[16:20], hex[20:])
@property
def bytes(self):
return self.int.to_bytes(16) # big endian
@property
def bytes_le(self):
bytes = self.bytes
return (bytes[4-1::-1] + bytes[6-1:4-1:-1] + bytes[8-1:6-1:-1] +
bytes[8:])
@property
def fields(self):
return (self.time_low, self.time_mid, self.time_hi_version,
self.clock_seq_hi_variant, self.clock_seq_low, self.node)
@property
def time_low(self):
return self.int >> 96
@property
def time_mid(self):
return (self.int >> 80) & 0xffff
@property
def time_hi_version(self):
return (self.int >> 64) & 0xffff
@property
def clock_seq_hi_variant(self):
return (self.int >> 56) & 0xff
@property
def clock_seq_low(self):
return (self.int >> 48) & 0xff
@property
def time(self):
return (((self.time_hi_version & 0x0fff) << 48) |
(self.time_mid << 32) | self.time_low)
@property
def clock_seq(self):
return (((self.clock_seq_hi_variant & 0x3f) << 8) |
self.clock_seq_low)
@property
def node(self):
return self.int & 0xffffffffffff
@property
def hex(self):
return '%032x' % self.int
@property
def urn(self):
return 'urn:uuid:' + str(self)
@property
def variant(self):
if not self.int & (0x8000 << 48):
return RESERVED_NCS
elif not self.int & (0x4000 << 48):
return RFC_4122
elif not self.int & (0x2000 << 48):
return RESERVED_MICROSOFT
else:
return RESERVED_FUTURE
@property
def version(self):
# The version bits are only meaningful for RFC 4122 UUIDs.
if self.variant == RFC_4122:
return int((self.int >> 76) & 0xf)
def _get_command_stdout(command, *args):
import io, os, shutil, subprocess
try:
path_dirs = os.environ.get('PATH', os.defpath).split(os.pathsep)
path_dirs.extend(['/sbin', '/usr/sbin'])
executable = shutil.which(command, path=os.pathsep.join(path_dirs))
if executable is None:
return None
# LC_ALL=C to ensure English output, stderr=DEVNULL to prevent output
# on stderr (Note: we don't have an example where the words we search
# for are actually localized, but in theory some system could do so.)
env = dict(os.environ)
env['LC_ALL'] = 'C'
proc = subprocess.Popen((executable,) + args,
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL,
env=env)
if not proc:
return None
stdout, stderr = proc.communicate()
return io.BytesIO(stdout)
except (OSError, subprocess.SubprocessError):
return None
# For MAC (a.k.a. IEEE 802, or EUI-48) addresses, the second least significant
# bit of the first octet signifies whether the MAC address is universally (0)
# or locally (1) administered. Network cards from hardware manufacturers will
# always be universally administered to guarantee global uniqueness of the MAC
# address, but any particular machine may have other interfaces which are
# locally administered. An example of the latter is the bridge interface to
# the Touch Bar on MacBook Pros.
#
# This bit works out to be the 42nd bit counting from 1 being the least
# significant, or 1<<41. We'll prefer universally administered MAC addresses
# over locally administered ones since the former are globally unique, but
# we'll return the first of the latter found if that's all the machine has.
#
# See https://en.wikipedia.org/wiki/MAC_address#Universal_vs._local
def _is_universal(mac):
return not (mac & (1 << 41))
def _find_mac_near_keyword(command, args, keywords, get_word_index):
"""Searches a command's output for a MAC address near a keyword.
Each line of words in the output is case-insensitively searched for
any of the given keywords. Upon a match, get_word_index is invoked
to pick a word from the line, given the index of the match. For
example, lambda i: 0 would get the first word on the line, while
lambda i: i - 1 would get the word preceding the keyword.
"""
stdout = _get_command_stdout(command, args)
if stdout is None:
return None
first_local_mac = None
for line in stdout:
words = line.lower().rstrip().split()
for i in range(len(words)):
if words[i] in keywords:
try:
word = words[get_word_index(i)]
mac = int(word.replace(_MAC_DELIM, b''), 16)
except (ValueError, IndexError):
# Virtual interfaces, such as those provided by
# VPNs, do not have a colon-delimited MAC address
# as expected, but a 16-byte HWAddr separated by
# dashes. These should be ignored in favor of a
# real MAC address
pass
else:
if _is_universal(mac):
return mac
first_local_mac = first_local_mac or mac
return first_local_mac or None
def _parse_mac(word):
# Accept 'HH:HH:HH:HH:HH:HH' MAC address (ex: '52:54:00:9d:0e:67'),
# but reject IPv6 address (ex: 'fe80::5054:ff:fe9' or '123:2:3:4:5:6:7:8').
#
# Virtual interfaces, such as those provided by VPNs, do not have a
# colon-delimited MAC address as expected, but a 16-byte HWAddr separated
# by dashes. These should be ignored in favor of a real MAC address
parts = word.split(_MAC_DELIM)
if len(parts) != 6:
return
if _MAC_OMITS_LEADING_ZEROES:
# (Only) on AIX the macaddr value given is not prefixed by 0, e.g.
# en0 1500 link#2 fa.bc.de.f7.62.4 110854824 0 160133733 0 0
# not
# en0 1500 link#2 fa.bc.de.f7.62.04 110854824 0 160133733 0 0
if not all(1 <= len(part) <= 2 for part in parts):
return
hexstr = b''.join(part.rjust(2, b'0') for part in parts)
else:
if not all(len(part) == 2 for part in parts):
return
hexstr = b''.join(parts)
try:
return int(hexstr, 16)
except ValueError:
return
def _find_mac_under_heading(command, args, heading):
"""Looks for a MAC address under a heading in a command's output.
The first line of words in the output is searched for the given
heading. Words at the same word index as the heading in subsequent
lines are then examined to see if they look like MAC addresses.
"""
stdout = _get_command_stdout(command, args)
if stdout is None:
return None
keywords = stdout.readline().rstrip().split()
try:
column_index = keywords.index(heading)
except ValueError:
return None
first_local_mac = None
for line in stdout:
words = line.rstrip().split()
try:
word = words[column_index]
except IndexError:
continue
mac = _parse_mac(word)
if mac is None:
continue
if _is_universal(mac):
return mac
if first_local_mac is None:
first_local_mac = mac
return first_local_mac
# The following functions call external programs to 'get' a macaddr value to
# be used as basis for an uuid
def _ifconfig_getnode():
"""Get the hardware address on Unix by running ifconfig."""
# This works on Linux ('' or '-a'), Tru64 ('-av'), but not all Unixes.
keywords = (b'hwaddr', b'ether', b'address:', b'lladdr')
for args in ('', '-a', '-av'):
mac = _find_mac_near_keyword('ifconfig', args, keywords, lambda i: i+1)
if mac:
return mac
return None
def _ip_getnode():
"""Get the hardware address on Unix by running ip."""
# This works on Linux with iproute2.
mac = _find_mac_near_keyword('ip', 'link', [b'link/ether'], lambda i: i+1)
if mac:
return mac
return None
def _arp_getnode():
"""Get the hardware address on Unix by running arp."""
import os, socket
if not hasattr(socket, "gethostbyname"):
return None
try:
ip_addr = socket.gethostbyname(socket.gethostname())
except OSError:
return None
# Try getting the MAC addr from arp based on our IP address (Solaris).
mac = _find_mac_near_keyword('arp', '-an', [os.fsencode(ip_addr)], lambda i: -1)
if mac:
return mac
# This works on OpenBSD
mac = _find_mac_near_keyword('arp', '-an', [os.fsencode(ip_addr)], lambda i: i+1)
if mac:
return mac
# This works on Linux, FreeBSD and NetBSD
mac = _find_mac_near_keyword('arp', '-an', [os.fsencode('(%s)' % ip_addr)],
lambda i: i+2)
# Return None instead of 0.
if mac:
return mac
return None
def _lanscan_getnode():
"""Get the hardware address on Unix by running lanscan."""
# This might work on HP-UX.
return _find_mac_near_keyword('lanscan', '-ai', [b'lan0'], lambda i: 0)
def _netstat_getnode():
"""Get the hardware address on Unix by running netstat."""
# This works on AIX and might work on Tru64 UNIX.
return _find_mac_under_heading('netstat', '-ian', b'Address')
def _ipconfig_getnode():
"""[DEPRECATED] Get the hardware address on Windows."""
# bpo-40501: UuidCreateSequential() is now the only supported approach
return _windll_getnode()
def _netbios_getnode():
"""[DEPRECATED] Get the hardware address on Windows."""
# bpo-40501: UuidCreateSequential() is now the only supported approach
return _windll_getnode()
# Import optional C extension at toplevel, to help disabling it when testing
try:
import _uuid
_generate_time_safe = getattr(_uuid, "generate_time_safe", None)
_UuidCreate = getattr(_uuid, "UuidCreate", None)
_has_uuid_generate_time_safe = _uuid.has_uuid_generate_time_safe
except ImportError:
_uuid = None
_generate_time_safe = None
_UuidCreate = None
_has_uuid_generate_time_safe = None
def _load_system_functions():
"""[DEPRECATED] Platform-specific functions loaded at import time"""
def _unix_getnode():
"""Get the hardware address on Unix using the _uuid extension module."""
if _generate_time_safe:
uuid_time, _ = _generate_time_safe()
return UUID(bytes=uuid_time).node
def _windll_getnode():
"""Get the hardware address on Windows using the _uuid extension module."""
if _UuidCreate:
uuid_bytes = _UuidCreate()
return UUID(bytes_le=uuid_bytes).node
def _random_getnode():
"""Get a random node ID."""
# RFC 4122, $4.1.6 says "For systems with no IEEE address, a randomly or
# pseudo-randomly generated value may be used; see Section 4.5. The
# multicast bit must be set in such addresses, in order that they will
# never conflict with addresses obtained from network cards."
#
# The "multicast bit" of a MAC address is defined to be "the least
# significant bit of the first octet". This works out to be the 41st bit
# counting from 1 being the least significant bit, or 1<<40.
#
# See https://en.wikipedia.org/wiki/MAC_address#Unicast_vs._multicast
import random
return random.getrandbits(48) | (1 << 40)
# _OS_GETTERS, when known, are targeted for a specific OS or platform.
# The order is by 'common practice' on the specified platform.
# Note: 'posix' and 'windows' _OS_GETTERS are prefixed by a dll/dlload() method
# which, when successful, means none of these "external" methods are called.
# _GETTERS is (also) used by test_uuid.py to SkipUnless(), e.g.,
# @unittest.skipUnless(_uuid._ifconfig_getnode in _uuid._GETTERS, ...)
if _LINUX:
_OS_GETTERS = [_ip_getnode, _ifconfig_getnode]
elif sys.platform == 'darwin':
_OS_GETTERS = [_ifconfig_getnode, _arp_getnode, _netstat_getnode]
elif sys.platform == 'win32':
# bpo-40201: _windll_getnode will always succeed, so these are not needed
_OS_GETTERS = []
elif _AIX:
_OS_GETTERS = [_netstat_getnode]
else:
_OS_GETTERS = [_ifconfig_getnode, _ip_getnode, _arp_getnode,
_netstat_getnode, _lanscan_getnode]
if os.name == 'posix':
_GETTERS = [_unix_getnode] + _OS_GETTERS
elif os.name == 'nt':
_GETTERS = [_windll_getnode] + _OS_GETTERS
else:
_GETTERS = _OS_GETTERS
_node = None
def getnode():
"""Get the hardware address as a 48-bit positive integer.
The first time this runs, it may launch a separate program, which could
be quite slow. If all attempts to obtain the hardware address fail, we
choose a random 48-bit number with its eighth bit set to 1 as recommended
in RFC 4122.
"""
global _node
if _node is not None:
return _node
for getter in _GETTERS + [_random_getnode]:
try:
_node = getter()
except:
continue
if (_node is not None) and (0 <= _node < (1 << 48)):
return _node
assert False, '_random_getnode() returned invalid value: {}'.format(_node)
_last_timestamp = None
def uuid1(node=None, clock_seq=None):
"""Generate a UUID from a host ID, sequence number, and the current time.
If 'node' is not given, getnode() is used to obtain the hardware
address. If 'clock_seq' is given, it is used as the sequence number;
otherwise a random 14-bit sequence number is chosen."""
# When the system provides a version-1 UUID generator, use it (but don't
# use UuidCreate here because its UUIDs don't conform to RFC 4122).
if _generate_time_safe is not None and node is clock_seq is None:
uuid_time, safely_generated = _generate_time_safe()
try:
is_safe = SafeUUID(safely_generated)
except ValueError:
is_safe = SafeUUID.unknown
return UUID(bytes=uuid_time, is_safe=is_safe)
global _last_timestamp
import time
nanoseconds = time.time_ns()
# 0x01b21dd213814000 is the number of 100-ns intervals between the
# UUID epoch 1582-10-15 00:00:00 and the Unix epoch 1970-01-01 00:00:00.
timestamp = nanoseconds // 100 + 0x01b21dd213814000
if _last_timestamp is not None and timestamp <= _last_timestamp:
timestamp = _last_timestamp + 1
_last_timestamp = timestamp
if clock_seq is None:
import random
clock_seq = random.getrandbits(14) # instead of stable storage
time_low = timestamp & 0xffffffff
time_mid = (timestamp >> 32) & 0xffff
time_hi_version = (timestamp >> 48) & 0x0fff
clock_seq_low = clock_seq & 0xff
clock_seq_hi_variant = (clock_seq >> 8) & 0x3f
if node is None:
node = getnode()
return UUID(fields=(time_low, time_mid, time_hi_version,
clock_seq_hi_variant, clock_seq_low, node), version=1)
def uuid3(namespace, name):
"""Generate a UUID from the MD5 hash of a namespace UUID and a name."""
from hashlib import md5
digest = md5(
namespace.bytes + bytes(name, "utf-8"),
usedforsecurity=False
).digest()
return UUID(bytes=digest[:16], version=3)
def uuid4():
"""Generate a random UUID."""
return UUID(bytes=os.urandom(16), version=4)
def uuid5(namespace, name):
"""Generate a UUID from the SHA-1 hash of a namespace UUID and a name."""
from hashlib import sha1
hash = sha1(namespace.bytes + bytes(name, "utf-8")).digest()
return UUID(bytes=hash[:16], version=5)
# The following standard UUIDs are for use with uuid3() or uuid5().
NAMESPACE_DNS = UUID('6ba7b810-9dad-11d1-80b4-00c04fd430c8')
NAMESPACE_URL = UUID('6ba7b811-9dad-11d1-80b4-00c04fd430c8')
NAMESPACE_OID = UUID('6ba7b812-9dad-11d1-80b4-00c04fd430c8')
NAMESPACE_X500 = UUID('6ba7b814-9dad-11d1-80b4-00c04fd430c8')
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