1 

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

     3 ==================================================

     4 

     5 .. module:: uuid

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

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

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

     9 

    10 

    11 .. versionadded:: 2.5

    12 

    13 This module provides immutable :class:`UUID` objects (the :class:`UUID` class)

    14 and the functions :func:`uuid1`, :func:`uuid3`, :func:`uuid4`, :func:`uuid5` for

    15 generating version 1, 3, 4, and 5 UUIDs as specified in :rfc:`4122`.

    16 

    17 If all you want is a unique ID, you should probably call :func:`uuid1` or

    18 :func:`uuid4`.  Note that :func:`uuid1` may compromise privacy since it creates

    19 a UUID containing the computer's network address.  :func:`uuid4` creates a

    20 random UUID.

    21 

    22 

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

    24 

    25    Create a UUID from either a string of 32 hexadecimal digits, a string of 16

    26    bytes as the *bytes* argument, a string of 16 bytes in little-endian order as

    27    the *bytes_le* argument, a tuple of six integers (32-bit *time_low*, 16-bit

    28    *time_mid*, 16-bit *time_hi_version*, 8-bit *clock_seq_hi_variant*, 8-bit

    29    *clock_seq_low*, 48-bit *node*) as the *fields* argument, or a single 128-bit

    30    integer as the *int* argument.  When a string of hex digits is given, curly

    31    braces, hyphens, and a URN prefix are all optional.  For example, these

    32    expressions all yield the same UUID::

    33 

    34       UUID('{12345678-1234-5678-1234-567812345678}')

    35       UUID('12345678123456781234567812345678')

    36       UUID('urn:uuid:12345678-1234-5678-1234-567812345678')

    37       UUID(bytes='\x12\x34\x56\x78'*4)

    38       UUID(bytes_le='\x78\x56\x34\x12\x34\x12\x78\x56' +

    39                     '\x12\x34\x56\x78\x12\x34\x56\x78')

    40       UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))

    41       UUID(int=0x12345678123456781234567812345678)

    42 

    43    Exactly one of *hex*, *bytes*, *bytes_le*, *fields*, or *int* must be given.

    44    The *version* argument is optional; if given, the resulting UUID will have its

    45    variant and version number set according to RFC 4122, overriding bits in the

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

    47 

    48 :class:`UUID` instances have these read-only attributes:

    49 

    50 

    51 .. attribute:: UUID.bytes

    52 

    53    The UUID as a 16-byte string (containing the six integer fields in big-endian

    54    byte order).

    55 

    56 

    57 .. attribute:: UUID.bytes_le

    58 

    59    The UUID as a 16-byte string (with *time_low*, *time_mid*, and *time_hi_version*

    60    in little-endian byte order).

    61 

    62 

    63 .. attribute:: UUID.fields

    64 

    65    A tuple of the six integer fields of the UUID, which are also available as six

    66    individual attributes and two derived attributes:

    67 

    68    +------------------------------+-------------------------------+

    69    | Field                        | Meaning                       |

    70    +==============================+===============================+

    71    | :attr:`time_low`             | the first 32 bits of the UUID |

    72    +------------------------------+-------------------------------+

    73    | :attr:`time_mid`             | the next 16 bits of the UUID  |

    74    +------------------------------+-------------------------------+

    75    | :attr:`time_hi_version`      | the next 16 bits of the UUID  |

    76    +------------------------------+-------------------------------+

    77    | :attr:`clock_seq_hi_variant` | the next 8 bits of the UUID   |

    78    +------------------------------+-------------------------------+

    79    | :attr:`clock_seq_low`        | the next 8 bits of the UUID   |

    80    +------------------------------+-------------------------------+

    81    | :attr:`node`                 | the last 48 bits of the UUID  |

    82    +------------------------------+-------------------------------+

    83    | :attr:`time`                 | the 60-bit timestamp          |

    84    +------------------------------+-------------------------------+

    85    | :attr:`clock_seq`            | the 14-bit sequence number    |

    86    +------------------------------+-------------------------------+

    87 

    88 

    89 .. attribute:: UUID.hex

    90 

    91    The UUID as a 32-character hexadecimal string.

    92 

    93 

    94 .. attribute:: UUID.int

    95 

    96    The UUID as a 128-bit integer.

    97 

    98 

    99 .. attribute:: UUID.urn

   100 

   101    The UUID as a URN as specified in RFC 4122.

   102 

   103 

   104 .. attribute:: UUID.variant

   105 

   106    The UUID variant, which determines the internal layout of the UUID. This will be

   107    one of the integer constants :const:`RESERVED_NCS`, :const:`RFC_4122`,

   108    :const:`RESERVED_MICROSOFT`, or :const:`RESERVED_FUTURE`.

   109 

   110 

   111 .. attribute:: UUID.version

   112 

   113    The UUID version number (1 through 5, meaningful only when the variant is

   114    :const:`RFC_4122`).

   115 

   116 The :mod:`uuid` module defines the following functions:

   117 

   118 

   119 .. function:: getnode()

   120 

   121    Get the hardware address as a 48-bit positive integer.  The first time this

   122    runs, it may launch a separate program, which could be quite slow.  If all

   123    attempts to obtain the hardware address fail, we choose a random 48-bit number

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

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

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

   127 

   128 .. index:: single: getnode

   129 

   130 

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

   132 

   133    Generate a UUID from a host ID, sequence number, and the current time. If *node*

   134    is not given, :func:`getnode` is used to obtain the hardware address. If

   135    *clock_seq* is given, it is used as the sequence number; otherwise a random

   136    14-bit sequence number is chosen.

   137 

   138 .. index:: single: uuid1

   139 

   140 

   141 .. function:: uuid3(namespace, name)

   142 

   143    Generate a UUID based on the MD5 hash of a namespace identifier (which is a

   144    UUID) and a name (which is a string).

   145 

   146 .. index:: single: uuid3

   147 

   148 

   149 .. function:: uuid4()

   150 

   151    Generate a random UUID.

   152 

   153 .. index:: single: uuid4

   154 

   155 

   156 .. function:: uuid5(namespace, name)

   157 

   158    Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a

   159    UUID) and a name (which is a string).

   160 

   161 .. index:: single: uuid5

   162 

   163 The :mod:`uuid` module defines the following namespace identifiers for use with

   164 :func:`uuid3` or :func:`uuid5`.

   165 

   166 

   167 .. data:: NAMESPACE_DNS

   168 

   169    When this namespace is specified, the *name* string is a fully-qualified domain

   170    name.

   171 

   172 

   173 .. data:: NAMESPACE_URL

   174 

   175    When this namespace is specified, the *name* string is a URL.

   176 

   177 

   178 .. data:: NAMESPACE_OID

   179 

   180    When this namespace is specified, the *name* string is an ISO OID.

   181 

   182 

   183 .. data:: NAMESPACE_X500

   184 

   185    When this namespace is specified, the *name* string is an X.500 DN in DER or a

   186    text output format.

   187 

   188 The :mod:`uuid` module defines the following constants for the possible values

   189 of the :attr:`variant` attribute:

   190 

   191 

   192 .. data:: RESERVED_NCS

   193 

   194    Reserved for NCS compatibility.

   195 

   196 

   197 .. data:: RFC_4122

   198 

   199    Specifies the UUID layout given in :rfc:`4122`.

   200 

   201 

   202 .. data:: RESERVED_MICROSOFT

   203 

   204    Reserved for Microsoft compatibility.

   205 

   206 

   207 .. data:: RESERVED_FUTURE

   208 

   209    Reserved for future definition.

   210 

   211 

   212 .. seealso::

   213 

   214    :rfc:`4122` - A Universally Unique IDentifier (UUID) URN Namespace

   215       This specification defines a Uniform Resource Name namespace for UUIDs, the

   216       internal format of UUIDs, and methods of generating UUIDs.

   217 

   218 

   219 .. _uuid-example:

   220 

   221 Example

   222 -------

   223 

   224 Here are some examples of typical usage of the :mod:`uuid` module::

   225 

   226    >>> import uuid

   227 

   228    # make a UUID based on the host ID and current time

   229    >>> uuid.uuid1()

   230    UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

   231 

   232    # make a UUID using an MD5 hash of a namespace UUID and a name

   233    >>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')

   234    UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

   235 

   236    # make a random UUID

   237    >>> uuid.uuid4()

   238    UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

   239 

   240    # make a UUID using a SHA-1 hash of a namespace UUID and a name

   241    >>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')

   242    UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

   243 

   244    # make a UUID from a string of hex digits (braces and hyphens ignored)

   245    >>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')

   246 

   247    # convert a UUID to a string of hex digits in standard form

   248    >>> str(x)

   249    '00010203-0405-0607-0809-0a0b0c0d0e0f'

   250 

   251    # get the raw 16 bytes of the UUID

   252    >>> x.bytes

   253    '\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'

   254 

   255    # make a UUID from a 16-byte string

   256    >>> uuid.UUID(bytes=x.bytes)

   257    UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')

   258