import re


def is_uuid(text):
    """
    >>> is_uuid('13f79535-47bb-0310-9956-ffa450edef68')
    True
    >>> is_uuid('d670460b4b4aece5915caf5c68d12f560a9fe3e4')
    False
    >>> is_uuid('13z79535-47bb-0310-9956-ffa450edef68')
    False
    """

    return bool(re.match(r'''
        # https://tools.ietf.org/html/rfc4122#section-3
        [a-f0-9]{8}  -   # time-low
        [a-f0-9]{4}  -   # time-mid
        [a-f0-9]{4}  -   # time-high-and-version
        [a-f0-9]{4}  -   # clock-seq-and-reserved clock-seq-low
        [a-f0-9]{12}     # node
        $
    ''', text, re.VERBOSE))