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
13This module provides immutable :class:`UUID` objects (the :class:`UUID` class)
14and the functions :func:`uuid1`, :func:`uuid3`, :func:`uuid4`, :func:`uuid5` for
15generating version 1, 3, 4, and 5 UUIDs as specified in :rfc:`4122`.
16
17If 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
19a UUID containing the computer's network address.  :func:`uuid4` creates a
20random 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 in big-endian order as the *bytes* argument, a string of 16 bytes in
27   little-endian order as the *bytes_le* argument, a tuple of six integers
28   (32-bit *time_low*, 16-bit *time_mid*, 16-bit *time_hi_version*,
29   8-bit *clock_seq_hi_variant*, 8-bit *clock_seq_low*, 48-bit *node*) as the
30   *fields* argument, or a single 128-bit integer as the *int* argument.
31   When a string of hex digits is given, curly braces, hyphens,
32   and a URN prefix are all optional.  For example, these
33   expressions all yield the same UUID::
34
35      UUID('{12345678-1234-5678-1234-567812345678}')
36      UUID('12345678123456781234567812345678')
37      UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
38      UUID(bytes='\x12\x34\x56\x78'*4)
39      UUID(bytes_le='\x78\x56\x34\x12\x34\x12\x78\x56' +
40                    '\x12\x34\x56\x78\x12\x34\x56\x78')
41      UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
42      UUID(int=0x12345678123456781234567812345678)
43
44   Exactly one of *hex*, *bytes*, *bytes_le*, *fields*, or *int* must be given.
45   The *version* argument is optional; if given, the resulting UUID will have its
46   variant and version number set according to RFC 4122, overriding bits in the
47   given *hex*, *bytes*, *bytes_le*, *fields*, or *int*.
48
49:class:`UUID` instances have these read-only attributes:
50
51
52.. attribute:: UUID.bytes
53
54   The UUID as a 16-byte string (containing the six integer fields in big-endian
55   byte order).
56
57
58.. attribute:: UUID.bytes_le
59
60   The UUID as a 16-byte string (with *time_low*, *time_mid*, and *time_hi_version*
61   in little-endian byte order).
62
63
64.. attribute:: UUID.fields
65
66   A tuple of the six integer fields of the UUID, which are also available as six
67   individual attributes and two derived attributes:
68
69   +------------------------------+-------------------------------+
70   | Field                        | Meaning                       |
71   +==============================+===============================+
72   | :attr:`time_low`             | the first 32 bits of the UUID |
73   +------------------------------+-------------------------------+
74   | :attr:`time_mid`             | the next 16 bits of the UUID  |
75   +------------------------------+-------------------------------+
76   | :attr:`time_hi_version`      | the next 16 bits of the UUID  |
77   +------------------------------+-------------------------------+
78   | :attr:`clock_seq_hi_variant` | the next 8 bits of the UUID   |
79   +------------------------------+-------------------------------+
80   | :attr:`clock_seq_low`        | the next 8 bits of the UUID   |
81   +------------------------------+-------------------------------+
82   | :attr:`node`                 | the last 48 bits of the UUID  |
83   +------------------------------+-------------------------------+
84   | :attr:`time`                 | the 60-bit timestamp          |
85   +------------------------------+-------------------------------+
86   | :attr:`clock_seq`            | the 14-bit sequence number    |
87   +------------------------------+-------------------------------+
88
89
90.. attribute:: UUID.hex
91
92   The UUID as a 32-character hexadecimal string.
93
94
95.. attribute:: UUID.int
96
97   The UUID as a 128-bit integer.
98
99
100.. attribute:: UUID.urn
101
102   The UUID as a URN as specified in RFC 4122.
103
104
105.. attribute:: UUID.variant
106
107   The UUID variant, which determines the internal layout of the UUID. This will be
108   one of the constants :const:`RESERVED_NCS`, :const:`RFC_4122`,
109   :const:`RESERVED_MICROSOFT`, or :const:`RESERVED_FUTURE`.
110
111
112.. attribute:: UUID.version
113
114   The UUID version number (1 through 5, meaningful only when the variant is
115   :const:`RFC_4122`).
116
117The :mod:`uuid` module defines the following functions:
118
119
120.. function:: getnode()
121
122   Get the hardware address as a 48-bit positive integer.  The first time this
123   runs, it may launch a separate program, which could be quite slow.  If all
124   attempts to obtain the hardware address fail, we choose a random 48-bit number
125   with its eighth bit set to 1 as recommended in RFC 4122.  "Hardware address"
126   means the MAC address of a network interface, and on a machine with multiple
127   network interfaces the MAC address of any one of them may be returned.
128
129.. index:: single: getnode
130
131
132.. function:: uuid1([node[, clock_seq]])
133
134   Generate a UUID from a host ID, sequence number, and the current time. If *node*
135   is not given, :func:`getnode` is used to obtain the hardware address. If
136   *clock_seq* is given, it is used as the sequence number; otherwise a random
137   14-bit sequence number is chosen.
138
139.. index:: single: uuid1
140
141
142.. function:: uuid3(namespace, name)
143
144   Generate a UUID based on the MD5 hash of a namespace identifier (which is a
145   UUID) and a name (which is a string).
146
147.. index:: single: uuid3
148
149
150.. function:: uuid4()
151
152   Generate a random UUID.
153
154.. index:: single: uuid4
155
156
157.. function:: uuid5(namespace, name)
158
159   Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a
160   UUID) and a name (which is a string).
161
162.. index:: single: uuid5
163
164The :mod:`uuid` module defines the following namespace identifiers for use with
165:func:`uuid3` or :func:`uuid5`.
166
167
168.. data:: NAMESPACE_DNS
169
170   When this namespace is specified, the *name* string is a fully-qualified domain
171   name.
172
173
174.. data:: NAMESPACE_URL
175
176   When this namespace is specified, the *name* string is a URL.
177
178
179.. data:: NAMESPACE_OID
180
181   When this namespace is specified, the *name* string is an ISO OID.
182
183
184.. data:: NAMESPACE_X500
185
186   When this namespace is specified, the *name* string is an X.500 DN in DER or a
187   text output format.
188
189The :mod:`uuid` module defines the following constants for the possible values
190of the :attr:`variant` attribute:
191
192
193.. data:: RESERVED_NCS
194
195   Reserved for NCS compatibility.
196
197
198.. data:: RFC_4122
199
200   Specifies the UUID layout given in :rfc:`4122`.
201
202
203.. data:: RESERVED_MICROSOFT
204
205   Reserved for Microsoft compatibility.
206
207
208.. data:: RESERVED_FUTURE
209
210   Reserved for future definition.
211
212
213.. seealso::
214
215   :rfc:`4122` - A Universally Unique IDentifier (UUID) URN Namespace
216      This specification defines a Uniform Resource Name namespace for UUIDs, the
217      internal format of UUIDs, and methods of generating UUIDs.
218
219
220.. _uuid-example:
221
222Example
223-------
224
225Here are some examples of typical usage of the :mod:`uuid` module::
226
227   >>> import uuid
228
229   >>> # make a UUID based on the host ID and current time
230   >>> uuid.uuid1()
231   UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')
232
233   >>> # make a UUID using an MD5 hash of a namespace UUID and a name
234   >>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
235   UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')
236
237   >>> # make a random UUID
238   >>> uuid.uuid4()
239   UUID('16fd2706-8baf-433b-82eb-8c7fada847da')
240
241   >>> # make a UUID using a SHA-1 hash of a namespace UUID and a name
242   >>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
243   UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')
244
245   >>> # make a UUID from a string of hex digits (braces and hyphens ignored)
246   >>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')
247
248   >>> # convert a UUID to a string of hex digits in standard form
249   >>> str(x)
250   '00010203-0405-0607-0809-0a0b0c0d0e0f'
251
252   >>> # get the raw 16 bytes of the UUID
253   >>> x.bytes
254   '\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'
255
256   >>> # make a UUID from a 16-byte string
257   >>> uuid.UUID(bytes=x.bytes)
258   UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')
259
260