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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()
# make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, '')
# make a random UUID
>>> uuid.uuid4()
# make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, '')
# 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)
# get the raw 16 bytes of the UUID
>>> x.bytes
# make a UUID from a 16-byte string
>>> uuid.UUID(bytes=x.bytes)
__author__ = 'Ka-Ping Yee <>'
'reserved for NCS compatibility', 'specified in RFC 4122',
'reserved for Microsoft compatibility', 'reserved for future definition']
class UUID(object):
"""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,
version the UUID version number (1 through 5, meaningful only
when the variant is RFC_4122)
def __init__(self, hex=None, bytes=None, bytes_le=None, fields=None,
int=None, version=None):
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(bytes_le='\x78\x56\x34\x12\x34\x12\x78\x56' +
UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
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'.
if [hex, bytes, bytes_le, fields, int].count(None) != 4:
raise TypeError('need one of hex, bytes, bytes_le, fields, or int')
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 = long(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[3] + bytes_le[2] + bytes_le[1] + bytes_le[0] +
bytes_le[5] + bytes_le[4] + bytes_le[7] + bytes_le[6] +
if bytes is not None:
if len(bytes) != 16:
raise ValueError('bytes is not a 16-char string')
int = long(('%02x'*16) % tuple(map(ord, bytes)), 16)
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<<32L:
raise ValueError('field 1 out of range (need a 32-bit value)')
if not 0 <= time_mid < 1<<16L:
raise ValueError('field 2 out of range (need a 16-bit value)')
if not 0 <= time_hi_version < 1<<16L:
raise ValueError('field 3 out of range (need a 16-bit value)')
if not 0 <= clock_seq_hi_variant < 1<<8L:
raise ValueError('field 4 out of range (need an 8-bit value)')
if not 0 <= clock_seq_low < 1<<8L:
raise ValueError('field 5 out of range (need an 8-bit value)')
if not 0 <= node < 1<<48L:
raise ValueError('field 6 out of range (need a 48-bit value)')
clock_seq = (clock_seq_hi_variant << 8L) | clock_seq_low
int = ((time_low << 96L) | (time_mid << 80L) |
(time_hi_version << 64L) | (clock_seq << 48L) | node)
if int is not None:
if not 0 <= int < 1<<128L:
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 << 48L)
int |= 0x8000 << 48L
# Set the version number.
int &= ~(0xf000 << 64L)
int |= version << 76L
self.__dict__['int'] = int
def __cmp__(self, other):
if isinstance(other, UUID):
return cmp(,
return NotImplemented
def __hash__(self):
return hash(
def __int__(self):
def __repr__(self):
return 'UUID(%r)' % str(self)
def __setattr__(self, name, value):
raise TypeError('UUID objects are immutable')
def __str__(self):
hex = '%032x' %
return '%s-%s-%s-%s-%s' % (
hex[:8], hex[8:12], hex[12:16], hex[16:20], hex[20:])
def get_bytes(self):
bytes = ''
for shift in range(0, 128, 8):
bytes = chr(( >> shift) & 0xff) + bytes
return bytes
bytes = property(get_bytes)
def get_bytes_le(self):
bytes = self.bytes
return (bytes[3] + bytes[2] + bytes[1] + bytes[0] +
bytes[5] + bytes[4] + bytes[7] + bytes[6] + bytes[8:])
bytes_le = property(get_bytes_le)
def get_fields(self):
return (self.time_low, self.time_mid, self.time_hi_version,
self.clock_seq_hi_variant, self.clock_seq_low, self.node)
fields = property(get_fields)
def get_time_low(self):
return >> 96L
time_low = property(get_time_low)
def get_time_mid(self):
return ( >> 80L) & 0xffff
time_mid = property(get_time_mid)
def get_time_hi_version(self):
return ( >> 64L) & 0xffff
time_hi_version = property(get_time_hi_version)
def get_clock_seq_hi_variant(self):
return ( >> 56L) & 0xff
clock_seq_hi_variant = property(get_clock_seq_hi_variant)
def get_clock_seq_low(self):
return ( >> 48L) & 0xff
clock_seq_low = property(get_clock_seq_low)
def get_time(self):
return (((self.time_hi_version & 0x0fffL) << 48L) |
(self.time_mid << 32L) | self.time_low)
time = property(get_time)
def get_clock_seq(self):
return (((self.clock_seq_hi_variant & 0x3fL) << 8L) |
clock_seq = property(get_clock_seq)
def get_node(self):
return & 0xffffffffffff
node = property(get_node)
def get_hex(self):
return '%032x' %
hex = property(get_hex)
def get_urn(self):
return 'urn:uuid:' + str(self)
urn = property(get_urn)
def get_variant(self):
if not & (0x8000 << 48L):
elif not & (0x4000 << 48L):
return RFC_4122
elif not & (0x2000 << 48L):
variant = property(get_variant)
def get_version(self):
# The version bits are only meaningful for RFC 4122 UUIDs.
if self.variant == RFC_4122:
return int(( >> 76L) & 0xf)
version = property(get_version)
def _find_mac(command, args, hw_identifiers, get_index):
import os
for dir in ['', '/sbin/', '/usr/sbin']:
executable = os.path.join(dir, command)
if not os.path.exists(executable):
# LC_ALL to get English output, 2>/dev/null to
# prevent output on stderr
cmd = 'LC_ALL=C %s %s 2>/dev/null' % (executable, args)
with os.popen(cmd) as pipe:
for line in pipe:
words = line.lower().split()
for i in range(len(words)):
if words[i] in hw_identifiers:
return int(
words[get_index(i)].replace(':', ''), 16)
except IOError:
return None
def _ifconfig_getnode():
"""Get the hardware address on Unix by running ifconfig."""
# This works on Linux ('' or '-a'), Tru64 ('-av'), but not all Unixes.
for args in ('', '-a', '-av'):
mac = _find_mac('ifconfig', args, ['hwaddr', 'ether'], lambda i: i+1)
if mac:
return mac
import socket
ip_addr = socket.gethostbyname(socket.gethostname())
# Try getting the MAC addr from arp based on our IP address (Solaris).
mac = _find_mac('arp', '-an', [ip_addr], lambda i: -1)
if mac:
return mac
# This might work on HP-UX.
mac = _find_mac('lanscan', '-ai', ['lan0'], lambda i: 0)
if mac:
return mac
return None
def _ipconfig_getnode():
"""Get the hardware address on Windows by running ipconfig.exe."""
import os, re
dirs = ['', r'c:\windows\system32', r'c:\winnt\system32']
import ctypes
buffer = ctypes.create_string_buffer(300)
ctypes.windll.kernel32.GetSystemDirectoryA(buffer, 300)
dirs.insert(0, buffer.value.decode('mbcs'))
for dir in dirs:
pipe = os.popen(os.path.join(dir, 'ipconfig') + ' /all')
except IOError:
for line in pipe:
value = line.split(':')[-1].strip().lower()
if re.match('([0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):
return int(value.replace('-', ''), 16)
def _netbios_getnode():
"""Get the hardware address on Windows using NetBIOS calls.
See for details."""
import win32wnet, netbios
ncb = netbios.NCB()
ncb.Command = netbios.NCBENUM
ncb.Buffer = adapters = netbios.LANA_ENUM()
if win32wnet.Netbios(ncb) != 0:
for i in range(adapters.length):
ncb.Command = netbios.NCBRESET
ncb.Lana_num = ord(adapters.lana[i])
if win32wnet.Netbios(ncb) != 0:
ncb.Command = netbios.NCBASTAT
ncb.Lana_num = ord(adapters.lana[i])
ncb.Callname = '*'.ljust(16)
ncb.Buffer = status = netbios.ADAPTER_STATUS()
if win32wnet.Netbios(ncb) != 0:
bytes = map(ord, status.adapter_address)
return ((bytes[0]<<40L) + (bytes[1]<<32L) + (bytes[2]<<24L) +
(bytes[3]<<16L) + (bytes[4]<<8L) + bytes[5])
# Thanks to Thomas Heller for ctypes and for his help with its use here.
# If ctypes is available, use it to find system routines for UUID generation.
_uuid_generate_random = _uuid_generate_time = _UuidCreate = None
import ctypes, ctypes.util
# The uuid_generate_* routines are provided by libuuid on at least
# Linux and FreeBSD, and provided by libc on Mac OS X.
for libname in ['uuid', 'c']:
lib = ctypes.CDLL(ctypes.util.find_library(libname))
if hasattr(lib, 'uuid_generate_random'):
_uuid_generate_random = lib.uuid_generate_random
if hasattr(lib, 'uuid_generate_time'):
_uuid_generate_time = lib.uuid_generate_time
# The uuid_generate_* functions are broken on MacOS X 10.5, as noted
# in issue #8621 the function generates the same sequence of values
# in the parent process and all children created using fork (unless
# those children use exec as well).
# Assume that the uuid_generate functions are broken from 10.5 onward,
# the test can be adjusted when a later version is fixed.
import sys
if sys.platform == 'darwin':
import os
if int(os.uname()[2].split('.')[0]) >= 9:
_uuid_generate_random = _uuid_generate_time = None
# On Windows prior to 2000, UuidCreate gives a UUID containing the
# hardware address. On Windows 2000 and later, UuidCreate makes a
# random UUID and UuidCreateSequential gives a UUID containing the
# hardware address. These routines are provided by the RPC runtime.
# NOTE: at least on Tim's WinXP Pro SP2 desktop box, while the last
# 6 bytes returned by UuidCreateSequential are fixed, they don't appear
# to bear any relationship to the MAC address of any network device
# on the box.
lib = ctypes.windll.rpcrt4
lib = None
_UuidCreate = getattr(lib, 'UuidCreateSequential',
getattr(lib, 'UuidCreate', None))
def _unixdll_getnode():
"""Get the hardware address on Unix using ctypes."""
_buffer = ctypes.create_string_buffer(16)
return UUID(bytes=_buffer.raw).node
def _windll_getnode():
"""Get the hardware address on Windows using ctypes."""
_buffer = ctypes.create_string_buffer(16)
if _UuidCreate(_buffer) == 0:
return UUID(bytes=_buffer.raw).node
def _random_getnode():
"""Get a random node ID, with eighth bit set as suggested by RFC 4122."""
import random
return random.randrange(0, 1<<48L) | 0x010000000000L
_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
import sys
if sys.platform == 'win32':
getters = [_windll_getnode, _netbios_getnode, _ipconfig_getnode]
getters = [_unixdll_getnode, _ifconfig_getnode]
for getter in getters + [_random_getnode]:
_node = getter()
if _node is not None:
return _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 _uuid_generate_time and node is clock_seq is None:
_buffer = ctypes.create_string_buffer(16)
return UUID(bytes=_buffer.raw)
global _last_timestamp
import time
nanoseconds = int(time.time() * 1e9)
# 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 = int(nanoseconds//100) + 0x01b21dd213814000L
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.randrange(1<<14L) # instead of stable storage
time_low = timestamp & 0xffffffffL
time_mid = (timestamp >> 32L) & 0xffffL
time_hi_version = (timestamp >> 48L) & 0x0fffL
clock_seq_low = clock_seq & 0xffL
clock_seq_hi_variant = (clock_seq >> 8L) & 0x3fL
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
hash = md5(namespace.bytes + name).digest()
return UUID(bytes=hash[:16], version=3)
def uuid4():
"""Generate a random UUID."""
# When the system provides a version-4 UUID generator, use it.
if _uuid_generate_random:
_buffer = ctypes.create_string_buffer(16)
return UUID(bytes=_buffer.raw)
# Otherwise, get randomness from urandom or the 'random' module.
import os
return UUID(bytes=os.urandom(16), version=4)
import random
bytes = [chr(random.randrange(256)) for i in range(16)]
return UUID(bytes=bytes, 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 + name).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')