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ActivePython 2.6 Documentation

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20.15. uuid — UUID objects according to RFC 4122

New in version 2.5.

This module provides immutable UUID objects (the UUID class) and the functions uuid1(), uuid3(), uuid4(), uuid5() for generating version 1, 3, 4, and 5 UUIDs as specified in RFC 4122.

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.

class uuid.UUID([hex[, bytes[, bytes_le[, fields[, int[, version]]]]]])

Create a UUID from either a string of 32 hexadecimal digits, a string of 16 bytes as the bytes argument, a string of 16 bytes 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='\x12\x34\x56\x78'*4)
UUID(bytes_le='\x78\x56\x34\x12\x34\x12\x78\x56' +
              '\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 RFC 4122, overriding bits in the given hex, bytes, bytes_le, fields, or int.

UUID instances have these read-only attributes:

UUID.bytes
The UUID as a 16-byte string (containing the six integer fields in big-endian byte order).
UUID.bytes_le
The UUID as a 16-byte string (with time_low, time_mid, and time_hi_version in little-endian byte order).
UUID.fields

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

Field Meaning
time_low the first 32 bits of the UUID
time_mid the next 16 bits of the UUID
time_hi_version the next 16 bits of the UUID
clock_seq_hi_variant the next 8 bits of the UUID
clock_seq_low the next 8 bits of the UUID
node the last 48 bits of the UUID
time the 60-bit timestamp
clock_seq the 14-bit sequence number
UUID.hex
The UUID as a 32-character hexadecimal string.
UUID.int
The UUID as a 128-bit integer.
UUID.urn
The UUID as a URN as specified in RFC 4122.
UUID.variant
The UUID variant, which determines the internal layout of the UUID. This will be one of the integer constants RESERVED_NCS, RFC_4122, RESERVED_MICROSOFT, or RESERVED_FUTURE.
UUID.version
The UUID version number (1 through 5, meaningful only when the variant is RFC_4122).

The uuid module defines the following functions:

uuid.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 its eighth bit set to 1 as recommended in RFC 4122. “Hardware address” means the MAC address of a network interface, and on a machine with multiple network interfaces the MAC address of any one of them may be returned.
uuid.uuid1([node[, clock_seq]])
Generate a UUID from a host ID, sequence number, and the current time. If node is not given, getnode() is used to obtain the hardware address. If clock_seq is given, it is used as the sequence number; otherwise a random 14-bit sequence number is chosen.
uuid.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 string).
uuid.uuid4()
Generate a random UUID.
uuid.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 string).

The uuid module defines the following namespace identifiers for use with uuid3() or uuid5().

uuid.NAMESPACE_DNS
When this namespace is specified, the name string is a fully-qualified domain name.
uuid.NAMESPACE_URL
When this namespace is specified, the name string is a URL.
uuid.NAMESPACE_OID
When this namespace is specified, the name string is an ISO OID.
uuid.NAMESPACE_X500
When this namespace is specified, the name string is an X.500 DN in DER or a text output format.

The uuid module defines the following constants for the possible values of the variant attribute:

uuid.RESERVED_NCS
Reserved for NCS compatibility.
uuid.RFC_4122
Specifies the UUID layout given in RFC 4122.
uuid.RESERVED_MICROSOFT
Reserved for Microsoft compatibility.
uuid.RESERVED_FUTURE
Reserved for future definition.

See also

RFC 4122 - 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.

20.15.1. 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()
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
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'

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