# `!uuid` --- UUID objects according to `9562`

<div class="module" data-synopsis="UUID objects (universally unique identifiers) according to RFC 9562">

uuid

</div>

**Source code:** `Lib/uuid.py`

------------------------------------------------------------------------

This module provides immutable `UUID` objects (the `UUID` class) and `functions <uuid-factory-functions>` for generating UUIDs corresponding to a specific UUID version as specified in `9562` (which supersedes `4122`), for example, `uuid1` for UUID version 1, `uuid3` for UUID version 3, and so on. Note that UUID version 2 is deliberately omitted as it is outside the scope of the RFC.

If all you want is a unique ID, you should probably call `uuid1` or `uuid4`. Note that `uuid1` may compromise privacy since it creates a UUID containing the computer's network address. `uuid4` creates a random UUID.

Depending on support from the underlying platform, `uuid1` 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 `UUID` have an `~UUID.is_safe` attribute which relays any information about the UUID's safety, using this enumeration:

<div class="SafeUUID">

<div class="versionadded">

3.7

</div>

<div class="attribute">

SafeUUID.safe

The UUID was generated by the platform in a multiprocessing-safe way.

</div>

<div class="attribute">

SafeUUID.unsafe

The UUID was not generated in a multiprocessing-safe way.

</div>

<div class="attribute">

SafeUUID.unknown

The platform does not provide information on whether the UUID was generated safely or not.

</div>

</div>

<div class="UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=SafeUUID.unknown)">

Create a UUID from either a string of 32 hexadecimal digits, a 16-byte `bytes` object in big-endian order as the *bytes* argument, a 16-byte `bytes` object in little-endian order as the *bytes_le* argument, a tuple of six integers (32-bit *time_low*, 16-bit *time_mid*, 16-bit *time_hi_version*, 8-bit *clock_seq_hi_variant*, 8-bit *clock_seq_low*, 48-bit *node*) as the *fields* argument, or a single 128-bit integer as the *int* 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:

    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)

Exactly one of *hex*, *bytes*, *bytes_le*, *fields*, or *int* must be given. The *version* argument is optional; if given, the resulting UUID will have its variant and version number set according to `9562`, overriding bits in the given *hex*, *bytes*, *bytes_le*, *fields*, or *int*.

<div class="versionchanged">

next Passing an object other than `bytes` as *bytes* or *bytes_le* now consistently raises `TypeError`. Previously, some invalid inputs raised `AssertionError` or `ValueError`.

</div>

Comparison of UUID objects are made by way of comparing their `UUID.int` attributes. Comparison with a non-UUID object raises a `TypeError`.

`str(uuid)` returns a string in the form `12345678-1234-5678-1234-567812345678` where the 32 hexadecimal digits represent the UUID.

</div>

`UUID` instances have these read-only attributes:

<div class="attribute">

UUID.bytes

The UUID as a 16-byte `bytes` object (containing the six integer fields in big-endian byte order).

</div>

<div class="attribute">

UUID.bytes_le

The UUID as a 16-byte `bytes` object (with *time_low*, *time_mid*, and *time_hi_version* in little-endian byte order).

</div>

<div class="attribute">

UUID.fields

A tuple of the six integer fields of the UUID, which are also available as six individual attributes and two derived attributes:

</div>

<table>
<tbody>
<tr>
<td>Field</td>
<td>Meaning</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.time_low</p>
</div></td>
<td>The first 32 bits of the UUID. Only relevant to version 1.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.time_mid</p>
</div></td>
<td>The next 16 bits of the UUID. Only relevant to version 1.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.time_hi_version</p>
</div></td>
<td>The next 16 bits of the UUID. Only relevant to version 1.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.clock_seq_hi_variant</p>
</div></td>
<td>The next 8 bits of the UUID. Only relevant to versions 1 and 6.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.clock_seq_low</p>
</div></td>
<td>The next 8 bits of the UUID. Only relevant to versions 1 and 6.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.node</p>
</div></td>
<td>The last 48 bits of the UUID. Only relevant to version 1.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.time</p>
</div></td>
<td>The 60-bit timestamp as a count of 100-nanosecond intervals since Gregorian epoch (1582-10-15 00:00:00) for versions 1 and 6, or the 48-bit timestamp in milliseconds since Unix epoch (1970-01-01 00:00:00) for version 7.</td>
</tr>
<tr>
<td><div class="attribute">
<p>UUID.clock_seq</p>
</div></td>
<td>The 14-bit sequence number. Only relevant to versions 1 and 6.</td>
</tr>
</tbody>
</table>

<div class="attribute">

UUID.hex

The UUID as a 32-character lowercase hexadecimal string.

</div>

<div class="attribute">

UUID.int

The UUID as a 128-bit integer.

</div>

<div class="attribute">

UUID.urn

The UUID as a URN as specified in `9562`.

</div>

<div class="attribute">

UUID.variant

The UUID variant, which determines the internal layout of the UUID. This will be one of the constants `RESERVED_NCS`, `RFC_4122`, `RESERVED_MICROSOFT`, or `RESERVED_FUTURE`.

</div>

<div class="attribute">

UUID.version

The UUID version number (1 through 8, meaningful only when the variant is `RFC_4122`).

<div class="versionchanged">

3.14 Added UUID versions 6, 7 and 8.

</div>

</div>

<div class="attribute">

UUID.is_safe

An enumeration of `SafeUUID` which indicates whether the platform generated the UUID in a multiprocessing-safe way.

<div class="versionadded">

3.7

</div>

</div>

The `!uuid` module defines the following functions:

<div class="function">

getnode()

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 `4122`. "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 *unset*) will be preferred over locally administered MAC addresses, but with no other ordering guarantees.

<div class="versionchanged">

3.7 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.

</div>

</div>

<div id="uuid-factory-functions">

<div class="function">

uuid1(node=None, clock_seq=None)

Generate a UUID from a host ID, sequence number, and the current time according to `RFC 9562, §5.1 <9562#section-5.1>`.

When *node* is not specified, `getnode` is used to obtain the hardware address as a 48-bit positive integer. When a sequence number *clock_seq* is not specified, a pseudo-random 14-bit positive integer is generated.

If *node* or *clock_seq* exceed their expected bit count, only their least significant bits are kept.

</div>

</div>

<div class="function">

uuid3(namespace, name)

Generate a UUID based on the MD5 hash of a namespace identifier (which is a UUID) and a name (which is a `bytes` object or a string that will be encoded using UTF-8) according to `RFC 9562, §5.3 <9562#section-5.3>`.

</div>

<div class="function">

uuid4()

Generate a random UUID in a cryptographically-secure method according to `RFC 9562, §5.4 <9562#section-5.4>`.

</div>

<div class="function">

uuid5(namespace, name)

Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a UUID) and a name (which is a `bytes` object or a string that will be encoded using UTF-8) according to `RFC 9562, §5.5 <9562#section-5.5>`.

</div>

<div class="function">

uuid6(node=None, clock_seq=None)

Generate a UUID from a sequence number and the current time according to `RFC 9562, §5.6 <9562#section-5.6>`.

This is an alternative to `uuid1` to improve database locality.

When *node* is not specified, `getnode` is used to obtain the hardware address as a 48-bit positive integer. When a sequence number *clock_seq* is not specified, a pseudo-random 14-bit positive integer is generated.

If *node* or *clock_seq* exceed their expected bit count, only their least significant bits are kept.

<div class="versionadded">

3.14

</div>

</div>

<div class="function">

uuid7()

Generate a time-based UUID according to `RFC 9562, §5.7 <9562#section-5.7>`.

For portability across platforms lacking sub-millisecond precision, UUIDs produced by this function embed a 48-bit timestamp and use a 42-bit counter to guarantee monotonicity within a millisecond.

<div class="versionadded">

3.14

</div>

</div>

<div class="function">

uuid8(a=None, b=None, c=None)

Generate a pseudo-random UUID according to `RFC 9562, §5.8 <9562#section-5.8>`.

When specified, the parameters *a*, *b* and *c* are expected to be positive integers of 48, 12 and 62 bits respectively. If they exceed their expected bit count, only their least significant bits are kept; non-specified arguments are substituted for a pseudo-random integer of appropriate size.

By default, *a*, *b* and *c* are not generated by a cryptographically secure pseudo-random number generator (CSPRNG). Use `uuid4` when a UUID needs to be used in a security-sensitive context.

<div class="versionadded">

3.14

</div>

</div>

The `!uuid` module defines the following namespace identifiers for use with `uuid3` or `uuid5`.

<div class="data">

NAMESPACE_DNS

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

</div>

<div class="data">

NAMESPACE_URL

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

</div>

<div class="data">

NAMESPACE_OID

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

</div>

<div class="data">

NAMESPACE_X500

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

</div>

The `!uuid` module defines the following constants for the possible values of the `~UUID.variant` attribute:

<div class="data">

RESERVED_NCS

Reserved for NCS compatibility.

</div>

<div class="data">

RFC_4122

Specifies the UUID layout given in `4122`. This constant is kept for backward compatibility even though `4122` has been superseded by `9562`.

</div>

<div class="data">

RESERVED_MICROSOFT

Reserved for Microsoft compatibility.

</div>

<div class="data">

RESERVED_FUTURE

Reserved for future definition.

</div>

The `!uuid` module defines the special Nil and Max UUID values:

<div class="data">

NIL

A special form of UUID that is specified to have all 128 bits set to zero according to `RFC 9562, §5.9 <9562#section-5.9>`.

<div class="versionadded">

3.14

</div>

</div>

<div class="data">

MAX

A special form of UUID that is specified to have all 128 bits set to one according to `RFC 9562, §5.10 <9562#section-5.10>`.

<div class="versionadded">

3.14

</div>

</div>

<div class="seealso">

`9562` - A Universally Unique IDentifier (UUID) URN Namespace  
This specification defines a Uniform Resource Name namespace for UUIDs, the internal format of UUIDs, and methods of generating UUIDs.

</div>

## Command-Line Usage

<div class="versionadded">

3.12

</div>

The `!uuid` module can be executed as a script from the command line.

``` sh
python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n NAMESPACE] [-N NAME]
```

The following options are accepted:

<div class="program">

uuid

</div>

<div class="option">

`-h, --help`  

Show the help message and exit.

</div>

<div class="option">

`-u <uuid>`  

`--uuid <uuid>`  

Specify the function name to use to generate the uuid. By default `uuid4` is used.

<div class="versionchanged">

3.14 Allow generating UUID versions 6, 7 and 8.

</div>

</div>

<div class="option">

`-n <namespace>`  

`--namespace <namespace>`  

The namespace is a `UUID`, or `@ns` where `ns` is a well-known predefined UUID addressed by namespace name. Such as `@dns`, `@url`, `@oid`, and `@x500`. Only required for `uuid3` / `uuid5` functions.

</div>

<div class="option">

`-N <name>`  

`--name <name>`  

The name used as part of generating the uuid. Only required for `uuid3` / `uuid5` functions.

</div>

<div class="option">

`-C <num>`  

`--count <num>`  

Generate *num* fresh UUIDs.

<div class="versionadded">

3.14

</div>

</div>

## Example

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

    >>> import uuid

    >>> # make a UUID based on the host ID and current time
    >>> uuid.uuid1()  # doctest: +SKIP
    UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

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

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

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

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

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

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

    >>> # make a UUID from a 16-byte bytes object
    >>> uuid.UUID(bytes=x.bytes)
    UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')

    >>> # get the Nil UUID
    >>> uuid.NIL
    UUID('00000000-0000-0000-0000-000000000000')

    >>> # get the Max UUID
    >>> uuid.MAX
    UUID('ffffffff-ffff-ffff-ffff-ffffffffffff')

    >>> # same as UUIDv1 but with fields reordered to improve DB locality
    >>> uuid.uuid6()  # doctest: +SKIP
    UUID('1f0799c0-98b9-62db-92c6-a0d365b91053')

    >>> # get UUIDv7 creation (local) time as a timestamp in milliseconds
    >>> u = uuid.uuid7()
    >>> u.time  # doctest: +SKIP
    1743936859822

    >>> # get UUIDv7 creation (local) time as a datetime object
    >>> import datetime as dt
    >>> dt.datetime.fromtimestamp(u.time / 1000)  # doctest: +SKIP
    datetime.datetime(...)

    >>> # make a UUID with custom blocks
    >>> uuid.uuid8(0x12345678, 0x9abcdef0, 0x11223344)
    UUID('00001234-5678-8ef0-8000-000011223344')

## Command-Line Example

Here are some examples of typical usage of the `!uuid` command-line interface:

```
# 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

# generate 42 random UUIDs
$ python -m uuid -C 42
```