Doc/library/uuid.rst
!uuid --- UUID objects according to :rfc:9562.. module:: uuid :synopsis: UUID objects (universally unique identifiers) according to RFC 9562
Source code: :source:Lib/uuid.py
This module provides immutable :class:UUID objects (the :class:UUID class)
and :ref:functions <uuid-factory-functions> for generating UUIDs corresponding
to a specific UUID version as specified in :rfc:9562 (which supersedes :rfc:4122),
for example, :func:uuid1 for UUID version 1, :func:uuid3 for UUID version 3, and so on.
Note that UUID version 2 is deliberately omitted as it is outside the scope of the RFC.
If all you want is a unique ID, you should probably call :func:uuid1 or
:func:uuid4. Note that :func:uuid1 may compromise privacy since it creates
a UUID containing the computer's network address. :func:uuid4 creates a
random UUID.
Depending on support from the underlying platform, :func:uuid1 may or may
not return a "safe" UUID. A safe UUID is one which is generated using
synchronization methods that ensure no two processes can obtain the same
UUID. All instances of :class:UUID have an :attr:~UUID.is_safe attribute
which relays any information about the UUID's safety, using this enumeration:
.. class:: SafeUUID
.. versionadded:: 3.7
.. attribute:: SafeUUID.safe
The UUID was generated by the platform in a multiprocessing-safe way.
.. attribute:: SafeUUID.unsafe
The UUID was not generated in a multiprocessing-safe way.
.. attribute:: SafeUUID.unknown
The platform does not provide information on whether the UUID was
generated safely or not.
.. class:: UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=SafeUUID.unknown)
Create a UUID from either a string of 32 hexadecimal digits, a string of 16 bytes in big-endian order 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=b'\x12\x34\x56\x78'*4)
UUID(bytes_le=b'\x78\x56\x34\x12\x34\x12\x78\x56' +
b'\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 number set according to :rfc:9562, overriding bits in the
given hex, bytes, bytes_le, fields, or int.
Comparison of UUID objects are made by way of comparing their
:attr:UUID.int attributes. Comparison with a non-UUID object
raises a :exc:TypeError.
str(uuid) returns a string in the form
12345678-1234-5678-1234-567812345678 where the 32 hexadecimal digits
represent the UUID.
:class:UUID instances have these read-only attributes:
.. attribute:: UUID.bytes
The UUID as a 16-byte string (containing the six integer fields in big-endian byte order).
.. attribute:: UUID.bytes_le
The UUID as a 16-byte string (with time_low, time_mid, and time_hi_version in little-endian byte order).
.. attribute:: UUID.fields
A tuple of the six integer fields of the UUID, which are also available as six individual attributes and two derived attributes:
.. list-table::
.. attribute:: UUID.hex
The UUID as a 32-character lowercase hexadecimal string.
.. attribute:: UUID.int
The UUID as a 128-bit integer.
.. attribute:: UUID.urn
The UUID as a URN as specified in :rfc:9562.
.. attribute:: UUID.variant
The UUID variant, which determines the internal layout of the UUID. This will be
one of the constants :const:RESERVED_NCS, :const:RFC_4122,
:const:RESERVED_MICROSOFT, or :const:RESERVED_FUTURE.
.. attribute:: UUID.version
The UUID version number (1 through 8, meaningful only when the variant is
:const:RFC_4122).
.. versionchanged:: 3.14 Added UUID versions 6, 7 and 8.
.. attribute:: UUID.is_safe
An enumeration of :class:SafeUUID which indicates whether the platform
generated the UUID in a multiprocessing-safe way.
.. versionadded:: 3.7
The :mod:!uuid module defines the following functions:
.. function:: 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 the multicast bit (least significant bit of the first octet)
set to 1 as recommended in :rfc:4122. "Hardware address" means the MAC
address of a network interface. On a machine with multiple network
interfaces, universally administered MAC addresses (i.e. where the second
least significant bit of the first octet is unset) will be preferred over
locally administered MAC addresses, but with no other ordering guarantees.
.. versionchanged:: 3.7 Universally administered MAC addresses are preferred over locally administered MAC addresses, since the former are guaranteed to be globally unique, while the latter are not.
.. _uuid-factory-functions:
.. function:: uuid1(node=None, clock_seq=None)
Generate a UUID from a host ID, sequence number, and the current time
according to :rfc:RFC 9562, §5.1 <9562#section-5.1>.
When node is not specified, :func:getnode is used to obtain the hardware
address as a 48-bit positive integer. When a sequence number clock_seq is
not specified, a pseudo-random 14-bit positive integer is generated.
If node or clock_seq exceed their expected bit count, only their least significant bits are kept.
.. function:: uuid3(namespace, name)
Generate a UUID based on the MD5 hash of a namespace identifier (which is a
UUID) and a name (which is a :class:bytes object or a string
that will be encoded using UTF-8)
according to :rfc:RFC 9562, §5.3 <9562#section-5.3>.
.. function:: uuid4()
Generate a random UUID in a cryptographically-secure method
according to :rfc:RFC 9562, §5.4 <9562#section-5.4>.
.. function:: uuid5(namespace, name)
Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a
UUID) and a name (which is a :class:bytes object or a string
that will be encoded using UTF-8)
according to :rfc:RFC 9562, §5.5 <9562#section-5.5>.
.. function:: uuid6(node=None, clock_seq=None)
Generate a UUID from a sequence number and the current time according to
:rfc:RFC 9562, §5.6 <9562#section-5.6>.
This is an alternative to :func:uuid1 to improve database locality.
When node is not specified, :func:getnode is used to obtain the hardware
address as a 48-bit positive integer. When a sequence number clock_seq is
not specified, a pseudo-random 14-bit positive integer is generated.
If node or clock_seq exceed their expected bit count, only their least significant bits are kept.
.. versionadded:: 3.14
.. function:: uuid7()
Generate a time-based UUID according to
:rfc:RFC 9562, §5.7 <9562#section-5.7>.
For portability across platforms lacking sub-millisecond precision, UUIDs produced by this function embed a 48-bit timestamp and use a 42-bit counter to guarantee monotonicity within a millisecond.
.. versionadded:: 3.14
.. function:: uuid8(a=None, b=None, c=None)
Generate a pseudo-random UUID according to
:rfc:RFC 9562, §5.8 <9562#section-5.8>.
When specified, the parameters a, b and c are expected to be positive integers of 48, 12 and 62 bits respectively. If they exceed their expected bit count, only their least significant bits are kept; non-specified arguments are substituted for a pseudo-random integer of appropriate size.
By default, a, b and c are not generated by a cryptographically
secure pseudo-random number generator (CSPRNG). Use :func:uuid4 when
a UUID needs to be used in a security-sensitive context.
.. versionadded:: 3.14
The :mod:!uuid module defines the following namespace identifiers for use with
:func:uuid3 or :func:uuid5.
.. data:: NAMESPACE_DNS
When this namespace is specified, the name string is a fully qualified domain name.
.. data:: NAMESPACE_URL
When this namespace is specified, the name string is a URL.
.. data:: NAMESPACE_OID
When this namespace is specified, the name string is an ISO OID.
.. data:: NAMESPACE_X500
When this namespace is specified, the name string is an X.500 DN in DER or a text output format.
The :mod:!uuid module defines the following constants for the possible values
of the :attr:~UUID.variant attribute:
.. data:: RESERVED_NCS
Reserved for NCS compatibility.
.. data:: RFC_4122
Specifies the UUID layout given in :rfc:4122. This constant is kept
for backward compatibility even though :rfc:4122 has been superseded
by :rfc:9562.
.. data:: RESERVED_MICROSOFT
Reserved for Microsoft compatibility.
.. data:: RESERVED_FUTURE
Reserved for future definition.
The :mod:!uuid module defines the special Nil and Max UUID values:
.. data:: NIL
A special form of UUID that is specified to have all 128 bits set to zero
according to :rfc:RFC 9562, §5.9 <9562#section-5.9>.
.. versionadded:: 3.14
.. data:: MAX
A special form of UUID that is specified to have all 128 bits set to one
according to :rfc:RFC 9562, §5.10 <9562#section-5.10>.
.. versionadded:: 3.14
.. seealso::
:rfc:9562 - A Universally Unique IDentifier (UUID) URN Namespace
This specification defines a Uniform Resource Name namespace for UUIDs, the
internal format of UUIDs, and methods of generating UUIDs.
.. _uuid-cli:
.. versionadded:: 3.12
The :mod:!uuid module can be executed as a script from the command line.
.. code-block:: sh
python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n NAMESPACE] [-N NAME]
The following options are accepted:
.. program:: uuid
.. option:: -h, --help
Show the help message and exit.
.. option:: -u <uuid> --uuid <uuid>
Specify the function name to use to generate the uuid. By default :func:uuid4
is used.
.. versionchanged:: 3.14 Allow generating UUID versions 6, 7 and 8.
.. option:: -n <namespace> --namespace <namespace>
The namespace is a UUID, or @ns where ns is a well-known predefined UUID
addressed by namespace name. Such as @dns, @url, @oid, and @x500.
Only required for :func:uuid3 / :func:uuid5 functions.
.. option:: -N <name> --name <name>
The name used as part of generating the uuid. Only required for
:func:uuid3 / :func:uuid5 functions.
.. option:: -C <num> --count <num>
Generate num fresh UUIDs.
.. versionadded:: 3.14
.. _uuid-example:
Here are some examples of typical usage of the :mod:!uuid module::
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() 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')
get the Nil UUID
uuid.NIL UUID('00000000-0000-0000-0000-000000000000')
get the Max UUID
uuid.MAX UUID('ffffffff-ffff-ffff-ffff-ffffffffffff')
same as UUIDv1 but with fields reordered to improve DB locality
uuid.uuid6() # doctest: +SKIP UUID('1f0799c0-98b9-62db-92c6-a0d365b91053')
get UUIDv7 creation (local) time as a timestamp in milliseconds
u = uuid.uuid7() u.time # doctest: +SKIP 1743936859822
get UUIDv7 creation (local) time as a datetime object
import datetime as dt dt.datetime.fromtimestamp(u.time / 1000) # doctest: +SKIP datetime.datetime(...)
make a UUID with custom blocks
uuid.uuid8(0x12345678, 0x9abcdef0, 0x11223344) UUID('00001234-5678-8ef0-8000-000011223344')
.. _uuid-cli-example:
Here are some examples of typical usage of the :mod:!uuid command-line interface:
.. code-block:: shell
$ python -m uuid
$ python -m uuid -u uuid1
$ python -m uuid -u uuid5 -n @url -N example.com
$ python -m uuid -C 42