:mod:`uuid` --- UUID objects according to RFC 4122

==================================================

.. module:: uuid

   :synopsis: UUID objects (universally unique identifiers) according to RFC 4122

.. moduleauthor:: Ka-Ping Yee <ping@zesty.ca>

.. sectionauthor:: George Yoshida <quiver@users.sourceforge.net>

.. versionadded:: 2.5

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.

.. class:: UUID([hex[, bytes[, bytes_le[, fields[, int[, version]]]]]])

   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 number set according to RFC 4122, overriding bits in the

   given *hex*, *bytes*, *bytes_le*, *fields*, or *int*.

: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 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 integer 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`).

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 its eighth bit set to 1 as recommended in RFC 4122.  "Hardware address"

   means the MAC address of a network interface, and on a machine with multiple

   network interfaces the MAC address of any one of them may be returned.

.. index:: single: getnode

.. function:: uuid1([node[, clock_seq]])

   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-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

   '\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')