uuid.py is getting a 64 bit hardware address for the loopback adapter in High Sierra, specifically in _ifconfig_getnode(). The function expects a 48 bit mac address, but is instead getting 64 bits back and converting it to an int value that is too long for the subsequent call in uuid.py. Apple must have moved to using EUI-64 for the loopback adapters.

This is a sample output of the call to ifconfig that is being parsed:

b'lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384\n'
b'\toptions=1203<RXCSUM,TXCSUM,TXSTATUS,SW_TIMESTAMP>\n'
b'\tinet 127.0.0.1 netmask 0xff000000 \n'
b'\tinet6 ::1 prefixlen 128 \n'
b'\tlladdr 70:cd:60:ff:ab:cd:ef:12 \n'

As you can see, the lladdr is longer than the usual 48 bit mac address but is nontheless returned for the node value, which then triggers

ValueError('field 6 out of range (need a 48-bit value)')


Full traceback:


Traceback (most recent call last):
  File "/Users/andy/Desktop/test.py", line 3, in <module>
    str(uuid.uuid1())
  File "/usr/local/Cellar/python3/3.6.4_2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/uuid.py", line 607, in uuid1
    clock_seq_hi_variant, clock_seq_low, node), version=1)
  File "/usr/local/Cellar/python3/3.6.4_2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/uuid.py", line 168, in __init__
    raise ValueError('field 6 out of range (need a 48-bit value)')
ValueError: field 6 out of range (need a 48-bit value)