#import random
#from ipaddress import IPv6Network, IPv6Address

#ip_a = IPv6Network('2001:db8::/48') + random.getrandbits
#ip_n = IPv6Network(ip_a)
#ip_n.prefixlen = 64

#print (ip_a)
#print (ip_n)

from ipaddress import IPv6Network
import random

ula = IPv6Network("fd00::/8")
random_network = IPv6Network((
    ula.network_address + (random.getrandbits(64 - ula.prefixlen) << 64 ),
    64))