如何确定字符串是否是有效的v4 UUID？

I'm making a validator based on UUID generated by client browser, I use this to identify a certain type data that the user sends; and would like to validate that the UUID that client sends it is in fact a valid Version 4 UUID.

I found this PHP preg_match UUID v4, it's close but not exactly what I'm looking for. I wish to know if exists something similar to is_empty() or strtodate() Where if string is not valid Sends FALSE.

I could do based on the regular expression but I would like something more native to test it.

Any ideas?

Version 4 UUIDs have the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is any hexadecimal digit and y is one of 8, 9, A, or B.

^[0-9A-F]{8}-[0-9A-F]{4}-4[0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$

To allow lowercase letters, use i modifier →

$UUIDv4 = '/^[0-9A-F]{8}-[0-9A-F]{4}-4[0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i';
preg_match($UUIDv4, $value) or die('Not valid UUID');

I found this question while I was looking for a Python answer. To help people in the same situation, I've added the Python solution.

You can use the uuid module:

#!/usr/bin/env python

from uuid import UUID


def is_valid_uuid(uuid_to_test, version=4):
    """
    Check if uuid_to_test is a valid UUID.

    Parameters
    ----------
    uuid_to_test : str
    version : {1, 2, 3, 4}

    Returns
    -------
    `True` if uuid_to_test is a valid UUID, otherwise `False`.

    Examples
    --------
    >>> is_valid_uuid('c9bf9e57-1685-4c89-bafb-ff5af830be8a')
    True
    >>> is_valid_uuid('c9bf9e58')
    False
    """
    try:
        uuid_obj = UUID(uuid_to_test, version=version)
    except ValueError:
        return False

    return str(uuid_obj) == uuid_to_test


if __name__ == '__main__':
    import doctest
    doctest.testmod()

import re

UUID_PATTERN = re.compile(r'^[\da-f]{8}-([\da-f]{4}-){3}[\da-f]{12}$', re.IGNORECASE)
uuid = '20f5484b-88ae-49b0-8af0-3a389b4917dd'

if UUID_PATTERN.match(uuid):
    return True
else:
    return False

If you only need it for security (for example if you need to print it in a javascript code and you want to avoid XSS) it doesn't really matter the position of the dashes, so it's just:

 /^[a-z0-9\-]{36}$/i

https://regex101.com/r/MDqB2Z/1

The existing answers all use regexIf you're using python, you might want to consider a try/except if you don't want to use regex: (Bit shorter than the answer above).

Our validator would then be:

import uuid

def is_valid_uuid(val):
    try:
        uuid.UUID(str(val))
        return True
    except ValueError:
        return False

>>> is_valid_uuid(1)
False
>>> is_valid_uuid("123-UUID-wannabe")
False
>>> is_valid_uuid({"A":"b"})
False
>>> is_valid_uuid([1, 2, 3])
False
>>> is_valid_uuid(uuid.uuid4())
True
>>> is_valid_uuid(str(uuid.uuid4()))
True
>>> is_valid_uuid(uuid.uuid4().hex)
True
>>> is_valid_uuid(uuid.uuid3(uuid.NAMESPACE_DNS, 'example.net'))
True
>>> is_valid_uuid(uuid.uuid5(uuid.NAMESPACE_DNS, 'example.net'))
True