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Georg Brandl116aa622007-08-15 14:28:22 +00001:mod:`uuid` --- UUID objects according to RFC 4122
2==================================================
3
4.. module:: uuid
5 :synopsis: UUID objects (universally unique identifiers) according to RFC 4122
6.. moduleauthor:: Ka-Ping Yee <ping@zesty.ca>
7.. sectionauthor:: George Yoshida <quiver@users.sourceforge.net>
8
9
Georg Brandl116aa622007-08-15 14:28:22 +000010This module provides immutable :class:`UUID` objects (the :class:`UUID` class)
11and the functions :func:`uuid1`, :func:`uuid3`, :func:`uuid4`, :func:`uuid5` for
12generating version 1, 3, 4, and 5 UUIDs as specified in :rfc:`4122`.
13
14If all you want is a unique ID, you should probably call :func:`uuid1` or
15:func:`uuid4`. Note that :func:`uuid1` may compromise privacy since it creates
16a UUID containing the computer's network address. :func:`uuid4` creates a
17random UUID.
18
19
Georg Brandl7f01a132009-09-16 15:58:14 +000020.. class:: UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None)
Georg Brandl116aa622007-08-15 14:28:22 +000021
22 Create a UUID from either a string of 32 hexadecimal digits, a string of 16
23 bytes as the *bytes* argument, a string of 16 bytes in little-endian order as
24 the *bytes_le* argument, a tuple of six integers (32-bit *time_low*, 16-bit
25 *time_mid*, 16-bit *time_hi_version*, 8-bit *clock_seq_hi_variant*, 8-bit
26 *clock_seq_low*, 48-bit *node*) as the *fields* argument, or a single 128-bit
27 integer as the *int* argument. When a string of hex digits is given, curly
28 braces, hyphens, and a URN prefix are all optional. For example, these
29 expressions all yield the same UUID::
30
31 UUID('{12345678-1234-5678-1234-567812345678}')
32 UUID('12345678123456781234567812345678')
33 UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
Georg Brandl1d523e12009-12-19 18:23:28 +000034 UUID(bytes=b'\x12\x34\x56\x78'*4)
35 UUID(bytes_le=b'\x78\x56\x34\x12\x34\x12\x78\x56' +
36 b'\x12\x34\x56\x78\x12\x34\x56\x78')
Georg Brandl116aa622007-08-15 14:28:22 +000037 UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
38 UUID(int=0x12345678123456781234567812345678)
39
40 Exactly one of *hex*, *bytes*, *bytes_le*, *fields*, or *int* must be given.
41 The *version* argument is optional; if given, the resulting UUID will have its
42 variant and version number set according to RFC 4122, overriding bits in the
43 given *hex*, *bytes*, *bytes_le*, *fields*, or *int*.
44
Georg Brandl116aa622007-08-15 14:28:22 +000045
Georg Brandl7f01a132009-09-16 15:58:14 +000046:class:`UUID` instances have these read-only attributes:
Georg Brandl116aa622007-08-15 14:28:22 +000047
48.. attribute:: UUID.bytes
49
50 The UUID as a 16-byte string (containing the six integer fields in big-endian
51 byte order).
52
53
54.. attribute:: UUID.bytes_le
55
56 The UUID as a 16-byte string (with *time_low*, *time_mid*, and *time_hi_version*
57 in little-endian byte order).
58
59
60.. attribute:: UUID.fields
61
62 A tuple of the six integer fields of the UUID, which are also available as six
63 individual attributes and two derived attributes:
64
65 +------------------------------+-------------------------------+
66 | Field | Meaning |
67 +==============================+===============================+
68 | :attr:`time_low` | the first 32 bits of the UUID |
69 +------------------------------+-------------------------------+
70 | :attr:`time_mid` | the next 16 bits of the UUID |
71 +------------------------------+-------------------------------+
72 | :attr:`time_hi_version` | the next 16 bits of the UUID |
73 +------------------------------+-------------------------------+
74 | :attr:`clock_seq_hi_variant` | the next 8 bits of the UUID |
75 +------------------------------+-------------------------------+
76 | :attr:`clock_seq_low` | the next 8 bits of the UUID |
77 +------------------------------+-------------------------------+
78 | :attr:`node` | the last 48 bits of the UUID |
79 +------------------------------+-------------------------------+
80 | :attr:`time` | the 60-bit timestamp |
81 +------------------------------+-------------------------------+
82 | :attr:`clock_seq` | the 14-bit sequence number |
83 +------------------------------+-------------------------------+
84
85
86.. attribute:: UUID.hex
87
88 The UUID as a 32-character hexadecimal string.
89
90
91.. attribute:: UUID.int
92
93 The UUID as a 128-bit integer.
94
95
96.. attribute:: UUID.urn
97
98 The UUID as a URN as specified in RFC 4122.
99
100
101.. attribute:: UUID.variant
102
103 The UUID variant, which determines the internal layout of the UUID. This will be
104 one of the integer constants :const:`RESERVED_NCS`, :const:`RFC_4122`,
105 :const:`RESERVED_MICROSOFT`, or :const:`RESERVED_FUTURE`.
106
107
108.. attribute:: UUID.version
109
110 The UUID version number (1 through 5, meaningful only when the variant is
111 :const:`RFC_4122`).
112
113The :mod:`uuid` module defines the following functions:
114
115
116.. function:: getnode()
117
118 Get the hardware address as a 48-bit positive integer. The first time this
119 runs, it may launch a separate program, which could be quite slow. If all
120 attempts to obtain the hardware address fail, we choose a random 48-bit number
121 with its eighth bit set to 1 as recommended in RFC 4122. "Hardware address"
122 means the MAC address of a network interface, and on a machine with multiple
123 network interfaces the MAC address of any one of them may be returned.
124
125.. index:: single: getnode
126
127
Georg Brandl7f01a132009-09-16 15:58:14 +0000128.. function:: uuid1(node=None, clock_seq=None)
Georg Brandl116aa622007-08-15 14:28:22 +0000129
130 Generate a UUID from a host ID, sequence number, and the current time. If *node*
131 is not given, :func:`getnode` is used to obtain the hardware address. If
132 *clock_seq* is given, it is used as the sequence number; otherwise a random
133 14-bit sequence number is chosen.
134
135.. index:: single: uuid1
136
137
138.. function:: uuid3(namespace, name)
139
140 Generate a UUID based on the MD5 hash of a namespace identifier (which is a
141 UUID) and a name (which is a string).
142
143.. index:: single: uuid3
144
145
146.. function:: uuid4()
147
148 Generate a random UUID.
149
150.. index:: single: uuid4
151
152
153.. function:: uuid5(namespace, name)
154
155 Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a
156 UUID) and a name (which is a string).
157
158.. index:: single: uuid5
159
160The :mod:`uuid` module defines the following namespace identifiers for use with
161:func:`uuid3` or :func:`uuid5`.
162
163
164.. data:: NAMESPACE_DNS
165
166 When this namespace is specified, the *name* string is a fully-qualified domain
167 name.
168
169
170.. data:: NAMESPACE_URL
171
172 When this namespace is specified, the *name* string is a URL.
173
174
175.. data:: NAMESPACE_OID
176
177 When this namespace is specified, the *name* string is an ISO OID.
178
179
180.. data:: NAMESPACE_X500
181
182 When this namespace is specified, the *name* string is an X.500 DN in DER or a
183 text output format.
184
185The :mod:`uuid` module defines the following constants for the possible values
186of the :attr:`variant` attribute:
187
188
189.. data:: RESERVED_NCS
190
191 Reserved for NCS compatibility.
192
193
194.. data:: RFC_4122
195
196 Specifies the UUID layout given in :rfc:`4122`.
197
198
199.. data:: RESERVED_MICROSOFT
200
201 Reserved for Microsoft compatibility.
202
203
204.. data:: RESERVED_FUTURE
205
206 Reserved for future definition.
207
208
209.. seealso::
210
211 :rfc:`4122` - A Universally Unique IDentifier (UUID) URN Namespace
212 This specification defines a Uniform Resource Name namespace for UUIDs, the
213 internal format of UUIDs, and methods of generating UUIDs.
214
215
216.. _uuid-example:
217
218Example
219-------
220
221Here are some examples of typical usage of the :mod:`uuid` module::
222
223 >>> import uuid
224
225 # make a UUID based on the host ID and current time
226 >>> uuid.uuid1()
227 UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')
228
229 # make a UUID using an MD5 hash of a namespace UUID and a name
230 >>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
231 UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')
232
233 # make a random UUID
234 >>> uuid.uuid4()
235 UUID('16fd2706-8baf-433b-82eb-8c7fada847da')
236
237 # make a UUID using a SHA-1 hash of a namespace UUID and a name
238 >>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
239 UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')
240
241 # make a UUID from a string of hex digits (braces and hyphens ignored)
242 >>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')
243
244 # convert a UUID to a string of hex digits in standard form
245 >>> str(x)
246 '00010203-0405-0607-0809-0a0b0c0d0e0f'
247
248 # get the raw 16 bytes of the UUID
249 >>> x.bytes
Georg Brandl1d523e12009-12-19 18:23:28 +0000250 b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'
Georg Brandl116aa622007-08-15 14:28:22 +0000251
252 # make a UUID from a 16-byte string
253 >>> uuid.UUID(bytes=x.bytes)
254 UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')
255