304 lines
9.9 KiB
ReStructuredText
304 lines
9.9 KiB
ReStructuredText
:mod:`uuid` --- UUID objects according to :rfc:`4122`
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=====================================================
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.. module:: uuid
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:synopsis: UUID objects (universally unique identifiers) according to RFC 4122
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.. moduleauthor:: Ka-Ping Yee <ping@zesty.ca>
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.. sectionauthor:: George Yoshida <quiver@users.sourceforge.net>
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**Source code:** :source:`Lib/uuid.py`
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--------------
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This module provides immutable :class:`UUID` objects (the :class:`UUID` class)
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and the functions :func:`uuid1`, :func:`uuid3`, :func:`uuid4`, :func:`uuid5` for
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generating version 1, 3, 4, and 5 UUIDs as specified in :rfc:`4122`.
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If all you want is a unique ID, you should probably call :func:`uuid1` or
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:func:`uuid4`. Note that :func:`uuid1` may compromise privacy since it creates
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a UUID containing the computer's network address. :func:`uuid4` creates a
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random UUID.
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Depending on support from the underlying platform, :func:`uuid1` may or may
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not return a "safe" UUID. A safe UUID is one which is generated using
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synchronization methods that ensure no two processes can obtain the same
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UUID. All instances of :class:`UUID` have an :attr:`is_safe` attribute
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which relays any information about the UUID's safety, using this enumeration:
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.. class:: SafeUUID
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.. versionadded:: 3.7
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.. attribute:: SafeUUID.safe
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The UUID was generated by the platform in a multiprocessing-safe way.
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.. attribute:: SafeUUID.unsafe
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The UUID was not generated in a multiprocessing-safe way.
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.. attribute:: SafeUUID.unknown
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The platform does not provide information on whether the UUID was
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generated safely or not.
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.. class:: UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=SafeUUID.unknown)
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Create a UUID from either a string of 32 hexadecimal digits, a string of 16
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bytes in big-endian order as the *bytes* argument, a string of 16 bytes in
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little-endian order as the *bytes_le* argument, a tuple of six integers
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(32-bit *time_low*, 16-bit *time_mid*, 16-bit *time_hi_version*,
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8-bit *clock_seq_hi_variant*, 8-bit *clock_seq_low*, 48-bit *node*) as the
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*fields* argument, or a single 128-bit integer as the *int* argument.
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When a string of hex digits is given, curly braces, hyphens,
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and a URN prefix are all optional. For example, these
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expressions all yield the same UUID::
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UUID('{12345678-1234-5678-1234-567812345678}')
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UUID('12345678123456781234567812345678')
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UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
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UUID(bytes=b'\x12\x34\x56\x78'*4)
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UUID(bytes_le=b'\x78\x56\x34\x12\x34\x12\x78\x56' +
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b'\x12\x34\x56\x78\x12\x34\x56\x78')
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UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
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UUID(int=0x12345678123456781234567812345678)
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Exactly one of *hex*, *bytes*, *bytes_le*, *fields*, or *int* must be given.
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The *version* argument is optional; if given, the resulting UUID will have its
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variant and version number set according to :rfc:`4122`, overriding bits in the
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given *hex*, *bytes*, *bytes_le*, *fields*, or *int*.
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Comparison of UUID objects are made by way of comparing their
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:attr:`UUID.int` attributes. Comparison with a non-UUID object
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raises a :exc:`TypeError`.
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``str(uuid)`` returns a string in the form
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``12345678-1234-5678-1234-567812345678`` where the 32 hexadecimal digits
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represent the UUID.
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:class:`UUID` instances have these read-only attributes:
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.. attribute:: UUID.bytes
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The UUID as a 16-byte string (containing the six integer fields in big-endian
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byte order).
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.. attribute:: UUID.bytes_le
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The UUID as a 16-byte string (with *time_low*, *time_mid*, and *time_hi_version*
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in little-endian byte order).
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.. attribute:: UUID.fields
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A tuple of the six integer fields of the UUID, which are also available as six
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individual attributes and two derived attributes:
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+------------------------------+-------------------------------+
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| Field | Meaning |
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+==============================+===============================+
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| :attr:`time_low` | the first 32 bits of the UUID |
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+------------------------------+-------------------------------+
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| :attr:`time_mid` | the next 16 bits of the UUID |
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+------------------------------+-------------------------------+
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| :attr:`time_hi_version` | the next 16 bits of the UUID |
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+------------------------------+-------------------------------+
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| :attr:`clock_seq_hi_variant` | the next 8 bits of the UUID |
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+------------------------------+-------------------------------+
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| :attr:`clock_seq_low` | the next 8 bits of the UUID |
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+------------------------------+-------------------------------+
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| :attr:`node` | the last 48 bits of the UUID |
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+------------------------------+-------------------------------+
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| :attr:`time` | the 60-bit timestamp |
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+------------------------------+-------------------------------+
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| :attr:`clock_seq` | the 14-bit sequence number |
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+------------------------------+-------------------------------+
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.. attribute:: UUID.hex
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The UUID as a 32-character lowercase hexadecimal string.
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.. attribute:: UUID.int
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The UUID as a 128-bit integer.
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.. attribute:: UUID.urn
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The UUID as a URN as specified in :rfc:`4122`.
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.. attribute:: UUID.variant
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The UUID variant, which determines the internal layout of the UUID. This will be
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one of the constants :const:`RESERVED_NCS`, :const:`RFC_4122`,
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:const:`RESERVED_MICROSOFT`, or :const:`RESERVED_FUTURE`.
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.. attribute:: UUID.version
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The UUID version number (1 through 5, meaningful only when the variant is
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:const:`RFC_4122`).
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.. attribute:: UUID.is_safe
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An enumeration of :class:`SafeUUID` which indicates whether the platform
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generated the UUID in a multiprocessing-safe way.
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.. versionadded:: 3.7
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The :mod:`uuid` module defines the following functions:
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.. function:: getnode()
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Get the hardware address as a 48-bit positive integer. The first time this
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runs, it may launch a separate program, which could be quite slow. If all
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attempts to obtain the hardware address fail, we choose a random 48-bit
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number with the multicast bit (least significant bit of the first octet)
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set to 1 as recommended in :rfc:`4122`. "Hardware address" means the MAC
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address of a network interface. On a machine with multiple network
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interfaces, universally administered MAC addresses (i.e. where the second
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least significant bit of the first octet is *unset*) will be preferred over
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locally administered MAC addresses, but with no other ordering guarantees.
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.. versionchanged:: 3.7
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Universally administered MAC addresses are preferred over locally
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administered MAC addresses, since the former are guaranteed to be
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globally unique, while the latter are not.
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.. index:: single: getnode
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.. function:: uuid1(node=None, clock_seq=None)
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Generate a UUID from a host ID, sequence number, and the current time. If *node*
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is not given, :func:`getnode` is used to obtain the hardware address. If
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*clock_seq* is given, it is used as the sequence number; otherwise a random
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14-bit sequence number is chosen.
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.. index:: single: uuid1
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.. function:: uuid3(namespace, name)
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Generate a UUID based on the MD5 hash of a namespace identifier (which is a
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UUID) and a name (which is a string).
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.. index:: single: uuid3
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.. function:: uuid4()
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Generate a random UUID.
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.. index:: single: uuid4
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.. function:: uuid5(namespace, name)
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Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a
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UUID) and a name (which is a string).
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.. index:: single: uuid5
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The :mod:`uuid` module defines the following namespace identifiers for use with
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:func:`uuid3` or :func:`uuid5`.
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.. data:: NAMESPACE_DNS
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When this namespace is specified, the *name* string is a fully-qualified domain
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name.
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.. data:: NAMESPACE_URL
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When this namespace is specified, the *name* string is a URL.
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.. data:: NAMESPACE_OID
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When this namespace is specified, the *name* string is an ISO OID.
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.. data:: NAMESPACE_X500
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When this namespace is specified, the *name* string is an X.500 DN in DER or a
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text output format.
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The :mod:`uuid` module defines the following constants for the possible values
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of the :attr:`variant` attribute:
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.. data:: RESERVED_NCS
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Reserved for NCS compatibility.
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.. data:: RFC_4122
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Specifies the UUID layout given in :rfc:`4122`.
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.. data:: RESERVED_MICROSOFT
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Reserved for Microsoft compatibility.
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.. data:: RESERVED_FUTURE
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Reserved for future definition.
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.. seealso::
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:rfc:`4122` - A Universally Unique IDentifier (UUID) URN Namespace
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This specification defines a Uniform Resource Name namespace for UUIDs, the
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internal format of UUIDs, and methods of generating UUIDs.
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.. _uuid-example:
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Example
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-------
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Here are some examples of typical usage of the :mod:`uuid` module::
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>>> import uuid
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>>> # make a UUID based on the host ID and current time
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>>> uuid.uuid1()
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UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')
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>>> # make a UUID using an MD5 hash of a namespace UUID and a name
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>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
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UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')
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>>> # make a random UUID
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>>> uuid.uuid4()
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UUID('16fd2706-8baf-433b-82eb-8c7fada847da')
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>>> # make a UUID using a SHA-1 hash of a namespace UUID and a name
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>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
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UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')
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>>> # make a UUID from a string of hex digits (braces and hyphens ignored)
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>>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')
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>>> # convert a UUID to a string of hex digits in standard form
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>>> str(x)
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'00010203-0405-0607-0809-0a0b0c0d0e0f'
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>>> # get the raw 16 bytes of the UUID
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>>> x.bytes
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b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'
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>>> # make a UUID from a 16-byte string
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>>> uuid.UUID(bytes=x.bytes)
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UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')
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