path: root/devdocs/python~3.12/library%2Fuuid.html

 <span id="uuid-uuid-objects-according-to-rfc-4122"></span><h1>uuid — UUID objects according to RFC 4122</h1> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/uuid.py">Lib/uuid.py</a></p>  <p>This module provides immutable <a class="reference internal" href="#uuid.UUID" title="uuid.UUID"><code>UUID</code></a> objects (the <a class="reference internal" href="#uuid.UUID" title="uuid.UUID"><code>UUID</code></a> class) and the functions <a class="reference internal" href="#uuid.uuid1" title="uuid.uuid1"><code>uuid1()</code></a>, <a class="reference internal" href="#uuid.uuid3" title="uuid.uuid3"><code>uuid3()</code></a>, <a class="reference internal" href="#uuid.uuid4" title="uuid.uuid4"><code>uuid4()</code></a>, <a class="reference internal" href="#uuid.uuid5" title="uuid.uuid5"><code>uuid5()</code></a> for generating version 1, 3, 4, and 5 UUIDs as specified in <span class="target" id="index-1"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4122.html"><strong>RFC 4122</strong></a>.</p> <p>If all you want is a unique ID, you should probably call <a class="reference internal" href="#uuid.uuid1" title="uuid.uuid1"><code>uuid1()</code></a> or <a class="reference internal" href="#uuid.uuid4" title="uuid.uuid4"><code>uuid4()</code></a>. Note that <a class="reference internal" href="#uuid.uuid1" title="uuid.uuid1"><code>uuid1()</code></a> may compromise privacy since it creates a UUID containing the computer’s network address. <a class="reference internal" href="#uuid.uuid4" title="uuid.uuid4"><code>uuid4()</code></a> creates a random UUID.</p> <p>Depending on support from the underlying platform, <a class="reference internal" href="#uuid.uuid1" title="uuid.uuid1"><code>uuid1()</code></a> may or may not return a “safe” UUID. A safe UUID is one which is generated using synchronization methods that ensure no two processes can obtain the same UUID. All instances of <a class="reference internal" href="#uuid.UUID" title="uuid.UUID"><code>UUID</code></a> have an <a class="reference internal" href="#uuid.UUID.is_safe" title="uuid.UUID.is_safe"><code>is_safe</code></a> attribute which relays any information about the UUID’s safety, using this enumeration:</p> <dl class="py class"> <dt class="sig sig-object py" id="uuid.SafeUUID">
<code>class uuid.SafeUUID</code> </dt> <dd>
<div class="versionadded"> <p><span class="versionmodified added">New in version 3.7.</span></p> </div> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.SafeUUID.safe">
<code>safe</code> </dt> <dd>
<p>The UUID was generated by the platform in a multiprocessing-safe way.</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.SafeUUID.unsafe">
<code>unsafe</code> </dt> <dd>
<p>The UUID was not generated in a multiprocessing-safe way.</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.SafeUUID.unknown">
<code>unknown</code> </dt> <dd>
<p>The platform does not provide information on whether the UUID was generated safely or not.</p> </dd>
</dl> </dd>
</dl> <dl class="py class"> <dt class="sig sig-object py" id="uuid.UUID">
<code>class uuid.UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=SafeUUID.unknown)</code> </dt> <dd>
<p>Create a UUID from either a string of 32 hexadecimal digits, a string of 16 bytes in big-endian order as the <em>bytes</em> argument, a string of 16 bytes in little-endian order as the <em>bytes_le</em> argument, a tuple of six integers (32-bit <em>time_low</em>, 16-bit <em>time_mid</em>, 16-bit <em>time_hi_version</em>, 8-bit <em>clock_seq_hi_variant</em>, 8-bit <em>clock_seq_low</em>, 48-bit <em>node</em>) as the <em>fields</em> argument, or a single 128-bit integer as the <em>int</em> 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:</p> <pre data-language="python">UUID('{12345678-1234-5678-1234-567812345678}')
UUID('12345678123456781234567812345678')
UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
UUID(bytes=b'\x12\x34\x56\x78'*4)
UUID(bytes_le=b'\x78\x56\x34\x12\x34\x12\x78\x56' +
              b'\x12\x34\x56\x78\x12\x34\x56\x78')
UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
UUID(int=0x12345678123456781234567812345678)
</pre> <p>Exactly one of <em>hex</em>, <em>bytes</em>, <em>bytes_le</em>, <em>fields</em>, or <em>int</em> must be given. The <em>version</em> argument is optional; if given, the resulting UUID will have its variant and version number set according to <span class="target" id="index-2"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4122.html"><strong>RFC 4122</strong></a>, overriding bits in the given <em>hex</em>, <em>bytes</em>, <em>bytes_le</em>, <em>fields</em>, or <em>int</em>.</p> <p>Comparison of UUID objects are made by way of comparing their <a class="reference internal" href="#uuid.UUID.int" title="uuid.UUID.int"><code>UUID.int</code></a> attributes. Comparison with a non-UUID object raises a <a class="reference internal" href="exceptions#TypeError" title="TypeError"><code>TypeError</code></a>.</p> <p><code>str(uuid)</code> returns a string in the form <code>12345678-1234-5678-1234-567812345678</code> where the 32 hexadecimal digits represent the UUID.</p> </dd>
</dl> <p><a class="reference internal" href="#uuid.UUID" title="uuid.UUID"><code>UUID</code></a> instances have these read-only attributes:</p> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.bytes">
<code>UUID.bytes</code> </dt> <dd>
<p>The UUID as a 16-byte string (containing the six integer fields in big-endian byte order).</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.bytes_le">
<code>UUID.bytes_le</code> </dt> <dd>
<p>The UUID as a 16-byte string (with <em>time_low</em>, <em>time_mid</em>, and <em>time_hi_version</em> in little-endian byte order).</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.fields">
<code>UUID.fields</code> </dt> <dd>
<p>A tuple of the six integer fields of the UUID, which are also available as six individual attributes and two derived attributes:</p> </dd>
</dl> <table class="docutils align-default">   <tr>
<td><p>Field</p></td> <td><p>Meaning</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.time_low">
<code>UUID.time_low</code> </dt> <dd></dd>
</dl> </td> <td><p>The first 32 bits of the UUID.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.time_mid">
<code>UUID.time_mid</code> </dt> <dd></dd>
</dl> </td> <td><p>The next 16 bits of the UUID.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.time_hi_version">
<code>UUID.time_hi_version</code> </dt> <dd></dd>
</dl> </td> <td><p>The next 16 bits of the UUID.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.clock_seq_hi_variant">
<code>UUID.clock_seq_hi_variant</code> </dt> <dd></dd>
</dl> </td> <td><p>The next 8 bits of the UUID.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.clock_seq_low">
<code>UUID.clock_seq_low</code> </dt> <dd></dd>
</dl> </td> <td><p>The next 8 bits of the UUID.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.node">
<code>UUID.node</code> </dt> <dd></dd>
</dl> </td> <td><p>The last 48 bits of the UUID.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.time">
<code>UUID.time</code> </dt> <dd></dd>
</dl> </td> <td><p>The 60-bit timestamp.</p></td> </tr> <tr>
<td>
<dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.clock_seq">
<code>UUID.clock_seq</code> </dt> <dd></dd>
</dl> </td> <td><p>The 14-bit sequence number.</p></td> </tr>  </table> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.hex">
<code>UUID.hex</code> </dt> <dd>
<p>The UUID as a 32-character lowercase hexadecimal string.</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.int">
<code>UUID.int</code> </dt> <dd>
<p>The UUID as a 128-bit integer.</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.urn">
<code>UUID.urn</code> </dt> <dd>
<p>The UUID as a URN as specified in <span class="target" id="index-3"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4122.html"><strong>RFC 4122</strong></a>.</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.variant">
<code>UUID.variant</code> </dt> <dd>
<p>The UUID variant, which determines the internal layout of the UUID. This will be one of the constants <a class="reference internal" href="#uuid.RESERVED_NCS" title="uuid.RESERVED_NCS"><code>RESERVED_NCS</code></a>, <a class="reference internal" href="#uuid.RFC_4122" title="uuid.RFC_4122"><code>RFC_4122</code></a>, <a class="reference internal" href="#uuid.RESERVED_MICROSOFT" title="uuid.RESERVED_MICROSOFT"><code>RESERVED_MICROSOFT</code></a>, or <a class="reference internal" href="#uuid.RESERVED_FUTURE" title="uuid.RESERVED_FUTURE"><code>RESERVED_FUTURE</code></a>.</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.version">
<code>UUID.version</code> </dt> <dd>
<p>The UUID version number (1 through 5, meaningful only when the variant is <a class="reference internal" href="#uuid.RFC_4122" title="uuid.RFC_4122"><code>RFC_4122</code></a>).</p> </dd>
</dl> <dl class="py attribute"> <dt class="sig sig-object py" id="uuid.UUID.is_safe">
<code>UUID.is_safe</code> </dt> <dd>
<p>An enumeration of <a class="reference internal" href="#uuid.SafeUUID" title="uuid.SafeUUID"><code>SafeUUID</code></a> which indicates whether the platform generated the UUID in a multiprocessing-safe way.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.7.</span></p> </div> </dd>
</dl> <p>The <a class="reference internal" href="#module-uuid" title="uuid: UUID objects (universally unique identifiers) according to RFC 4122"><code>uuid</code></a> module defines the following functions:</p> <dl class="py function"> <dt class="sig sig-object py" id="uuid.getnode">
<code>uuid.getnode()</code> </dt> <dd>
<p>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 the multicast bit (least significant bit of the first octet) set to 1 as recommended in <span class="target" id="index-4"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4122.html"><strong>RFC 4122</strong></a>. “Hardware address” means the MAC address of a network interface. On a machine with multiple network interfaces, universally administered MAC addresses (i.e. where the second least significant bit of the first octet is <em>unset</em>) will be preferred over locally administered MAC addresses, but with no other ordering guarantees.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.7: </span>Universally administered MAC addresses are preferred over locally administered MAC addresses, since the former are guaranteed to be globally unique, while the latter are not.</p> </div> </dd>
</dl> <span class="target" id="index-5"></span><dl class="py function"> <dt class="sig sig-object py" id="uuid.uuid1">
<code>uuid.uuid1(node=None, clock_seq=None)</code> </dt> <dd>
<p>Generate a UUID from a host ID, sequence number, and the current time. If <em>node</em> is not given, <a class="reference internal" href="#uuid.getnode" title="uuid.getnode"><code>getnode()</code></a> is used to obtain the hardware address. If <em>clock_seq</em> is given, it is used as the sequence number; otherwise a random 14-bit sequence number is chosen.</p> </dd>
</dl> <span class="target" id="index-6"></span><dl class="py function"> <dt class="sig sig-object py" id="uuid.uuid3">
<code>uuid.uuid3(namespace, name)</code> </dt> <dd>
<p>Generate a UUID based on the MD5 hash of a namespace identifier (which is a UUID) and a name (which is a <a class="reference internal" href="stdtypes#bytes" title="bytes"><code>bytes</code></a> object or a string that will be encoded using UTF-8).</p> </dd>
</dl> <span class="target" id="index-7"></span><dl class="py function"> <dt class="sig sig-object py" id="uuid.uuid4">
<code>uuid.uuid4()</code> </dt> <dd>
<p>Generate a random UUID.</p> </dd>
</dl> <span class="target" id="index-8"></span><dl class="py function"> <dt class="sig sig-object py" id="uuid.uuid5">
<code>uuid.uuid5(namespace, name)</code> </dt> <dd>
<p>Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a UUID) and a name (which is a <a class="reference internal" href="stdtypes#bytes" title="bytes"><code>bytes</code></a> object or a string that will be encoded using UTF-8).</p> </dd>
</dl> <p id="index-9">The <a class="reference internal" href="#module-uuid" title="uuid: UUID objects (universally unique identifiers) according to RFC 4122"><code>uuid</code></a> module defines the following namespace identifiers for use with <a class="reference internal" href="#uuid.uuid3" title="uuid.uuid3"><code>uuid3()</code></a> or <a class="reference internal" href="#uuid.uuid5" title="uuid.uuid5"><code>uuid5()</code></a>.</p> <dl class="py data"> <dt class="sig sig-object py" id="uuid.NAMESPACE_DNS">
<code>uuid.NAMESPACE_DNS</code> </dt> <dd>
<p>When this namespace is specified, the <em>name</em> string is a fully qualified domain name.</p> </dd>
</dl> <dl class="py data"> <dt class="sig sig-object py" id="uuid.NAMESPACE_URL">
<code>uuid.NAMESPACE_URL</code> </dt> <dd>
<p>When this namespace is specified, the <em>name</em> string is a URL.</p> </dd>
</dl> <dl class="py data"> <dt class="sig sig-object py" id="uuid.NAMESPACE_OID">
<code>uuid.NAMESPACE_OID</code> </dt> <dd>
<p>When this namespace is specified, the <em>name</em> string is an ISO OID.</p> </dd>
</dl> <dl class="py data"> <dt class="sig sig-object py" id="uuid.NAMESPACE_X500">
<code>uuid.NAMESPACE_X500</code> </dt> <dd>
<p>When this namespace is specified, the <em>name</em> string is an X.500 DN in DER or a text output format.</p> </dd>
</dl> <p>The <a class="reference internal" href="#module-uuid" title="uuid: UUID objects (universally unique identifiers) according to RFC 4122"><code>uuid</code></a> module defines the following constants for the possible values of the <a class="reference internal" href="#uuid.UUID.variant" title="uuid.UUID.variant"><code>variant</code></a> attribute:</p> <dl class="py data"> <dt class="sig sig-object py" id="uuid.RESERVED_NCS">
<code>uuid.RESERVED_NCS</code> </dt> <dd>
<p>Reserved for NCS compatibility.</p> </dd>
</dl> <dl class="py data"> <dt class="sig sig-object py" id="uuid.RFC_4122">
<code>uuid.RFC_4122</code> </dt> <dd>
<p>Specifies the UUID layout given in <span class="target" id="index-10"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4122.html"><strong>RFC 4122</strong></a>.</p> </dd>
</dl> <dl class="py data"> <dt class="sig sig-object py" id="uuid.RESERVED_MICROSOFT">
<code>uuid.RESERVED_MICROSOFT</code> </dt> <dd>
<p>Reserved for Microsoft compatibility.</p> </dd>
</dl> <dl class="py data"> <dt class="sig sig-object py" id="uuid.RESERVED_FUTURE">
<code>uuid.RESERVED_FUTURE</code> </dt> <dd>
<p>Reserved for future definition.</p> </dd>
</dl> <div class="admonition seealso"> <p class="admonition-title">See also</p> <dl class="simple"> <dt>
<span class="target" id="index-11"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4122.html"><strong>RFC 4122</strong></a> - A Universally Unique IDentifier (UUID) URN Namespace</dt>
<dd>
<p>This specification defines a Uniform Resource Name namespace for UUIDs, the internal format of UUIDs, and methods of generating UUIDs.</p> </dd> </dl> </div> <section id="command-line-usage"> <span id="uuid-cli"></span><h2>Command-Line Usage</h2> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.12.</span></p> </div> <p>The <a class="reference internal" href="#module-uuid" title="uuid: UUID objects (universally unique identifiers) according to RFC 4122"><code>uuid</code></a> module can be executed as a script from the command line.</p> <pre data-language="sh">python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5}] [-n NAMESPACE] [-N NAME]
</pre> <p>The following options are accepted:</p> <dl class="std option"> <dt class="sig sig-object std" id="cmdoption-uuid-h">
<code>-h, --help</code> </dt> <dd>
<p>Show the help message and exit.</p> </dd>
</dl> <dl class="std option"> <dt class="sig sig-object std" id="cmdoption-uuid-u">
<code>-u &lt;uuid&gt;</code> </dt> <dt class="sig sig-object std" id="cmdoption-uuid-uuid">
<code>--uuid &lt;uuid&gt;</code> </dt> <dd>
<p>Specify the function name to use to generate the uuid. By default <a class="reference internal" href="#uuid.uuid4" title="uuid.uuid4"><code>uuid4()</code></a> is used.</p> </dd>
</dl> <dl class="std option"> <dt class="sig sig-object std" id="cmdoption-uuid-n">
<code>-n &lt;namespace&gt;</code> </dt> <dt class="sig sig-object std" id="cmdoption-uuid-namespace">
<code>--namespace &lt;namespace&gt;</code> </dt> <dd>
<p>The namespace is a <code>UUID</code>, or <code>@ns</code> where <code>ns</code> is a well-known predefined UUID addressed by namespace name. Such as <code>@dns</code>, <code>@url</code>, <code>@oid</code>, and <code>@x500</code>. Only required for <a class="reference internal" href="#uuid.uuid3" title="uuid.uuid3"><code>uuid3()</code></a> / <a class="reference internal" href="#uuid.uuid5" title="uuid.uuid5"><code>uuid5()</code></a> functions.</p> </dd>
</dl> <dl class="std option"> <dt class="sig sig-object std" id="cmdoption-uuid-N">
<code>-N &lt;name&gt;</code> </dt> <dt class="sig sig-object std" id="cmdoption-uuid-name">
<code>--name &lt;name&gt;</code> </dt> <dd>
<p>The name used as part of generating the uuid. Only required for <a class="reference internal" href="#uuid.uuid3" title="uuid.uuid3"><code>uuid3()</code></a> / <a class="reference internal" href="#uuid.uuid5" title="uuid.uuid5"><code>uuid5()</code></a> functions.</p> </dd>
</dl> </section> <section id="example"> <span id="uuid-example"></span><h2>Example</h2> <p>Here are some examples of typical usage of the <a class="reference internal" href="#module-uuid" title="uuid: UUID objects (universally unique identifiers) according to RFC 4122"><code>uuid</code></a> module:</p> <pre data-language="python">&gt;&gt;&gt; import uuid

&gt;&gt;&gt; # make a UUID based on the host ID and current time
&gt;&gt;&gt; uuid.uuid1()
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

&gt;&gt;&gt; # make a UUID using an MD5 hash of a namespace UUID and a name
&gt;&gt;&gt; uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

&gt;&gt;&gt; # make a random UUID
&gt;&gt;&gt; uuid.uuid4()
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

&gt;&gt;&gt; # make a UUID using a SHA-1 hash of a namespace UUID and a name
&gt;&gt;&gt; uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

&gt;&gt;&gt; # make a UUID from a string of hex digits (braces and hyphens ignored)
&gt;&gt;&gt; x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')

&gt;&gt;&gt; # convert a UUID to a string of hex digits in standard form
&gt;&gt;&gt; str(x)
'00010203-0405-0607-0809-0a0b0c0d0e0f'

&gt;&gt;&gt; # get the raw 16 bytes of the UUID
&gt;&gt;&gt; x.bytes
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'

&gt;&gt;&gt; # make a UUID from a 16-byte string
&gt;&gt;&gt; uuid.UUID(bytes=x.bytes)
UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')
</pre> </section> <section id="command-line-example"> <span id="uuid-cli-example"></span><h2>Command-Line Example</h2> <p>Here are some examples of typical usage of the <a class="reference internal" href="#module-uuid" title="uuid: UUID objects (universally unique identifiers) according to RFC 4122"><code>uuid</code></a> command line interface:</p> <pre data-language="shell"># generate a random uuid - by default uuid4() is used
$ python -m uuid

# generate a uuid using uuid1()
$ python -m uuid -u uuid1

# generate a uuid using uuid5
$ python -m uuid -u uuid5 -n @url -N example.com
</pre> </section> <div class="_attribution">
  <p class="_attribution-p">
    &copy; 2001&ndash;2023 Python Software Foundation<br>Licensed under the PSF License.<br>
    <a href="https://docs.python.org/3.12/library/uuid.html" class="_attribution-link">https://docs.python.org/3.12/library/uuid.html</a>
  </p>
</div>