:mod:`uuid` --- UUID objects according to :rfc:`4122` ===================================================== .. module:: uuid :synopsis: UUID objects (universally unique identifiers) according to RFC 4122 .. moduleauthor:: Ka-Ping Yee .. sectionauthor:: George Yoshida **Source code:** :source:`Lib/uuid.py` -------------- This module provides immutable :class:`UUID` objects (the :class:`UUID` class) and the functions :func:`uuid1`, :func:`uuid3`, :func:`uuid4`, :func:`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 :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:`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:`4122`, 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: +------------------------------+-------------------------------+ | Field | Meaning | +==============================+===============================+ | :attr:`time_low` | the first 32 bits of the UUID | +------------------------------+-------------------------------+ | :attr:`time_mid` | the next 16 bits of the UUID | +------------------------------+-------------------------------+ | :attr:`time_hi_version` | the next 16 bits of the UUID | +------------------------------+-------------------------------+ | :attr:`clock_seq_hi_variant` | the next 8 bits of the UUID | +------------------------------+-------------------------------+ | :attr:`clock_seq_low` | the next 8 bits of the UUID | +------------------------------+-------------------------------+ | :attr:`node` | the last 48 bits of the UUID | +------------------------------+-------------------------------+ | :attr:`time` | the 60-bit timestamp | +------------------------------+-------------------------------+ | :attr:`clock_seq` | the 14-bit sequence number | +------------------------------+-------------------------------+ .. 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:`4122`. .. 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 5, meaningful only when the variant is :const:`RFC_4122`). .. 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. .. index:: single: getnode .. function:: uuid1(node=None, clock_seq=None) Generate a UUID from a host ID, sequence number, and the current time. If *node* is not given, :func:`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. .. index:: single: uuid1 .. 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 string). .. index:: single: uuid3 .. function:: uuid4() Generate a random UUID. .. index:: single: uuid4 .. 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 string). .. index:: single: uuid5 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:`variant` attribute: .. data:: RESERVED_NCS Reserved for NCS compatibility. .. data:: RFC_4122 Specifies the UUID layout given in :rfc:`4122`. .. data:: RESERVED_MICROSOFT Reserved for Microsoft compatibility. .. data:: RESERVED_FUTURE Reserved for future definition. .. seealso:: :rfc:`4122` - 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: Command-Line Usage ------------------ .. 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}] [-n NAMESPACE] [-N NAME] The following options are accepted: .. program:: uuid .. cmdoption:: -h, --help Show the help message and exit. .. cmdoption:: -u --uuid Specify the function name to use to generate the uuid. By default :func:`uuid4` is used. .. cmdoption:: -n --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. .. cmdoption:: -N --name The name used as part of generating the uuid. Only required for :func:`uuid3` / :func:`uuid5` functions. .. _uuid-example: 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() 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') .. _uuid-cli-example: Command-Line Example -------------------- Here are some examples of typical usage of the :mod:`uuid` command line interface: .. code-block:: shell # generate a random uuid - by default uuid4() is used $ python -m uuid # generate a uuid using uuid1() $ python -m uuid -u uuid1 # generate a uuid using uuid5 $ python -m uuid -u uuid5 -n @url -N example.com