/Doc/library/uuid.rst
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- :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')