/Doc/library/uuid.rst

  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 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
116The :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
163The :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
188The :mod:`uuid` module defines the following constants for the possible values
189of 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
221Example
222-------
223
224Here 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