We can use the netifaces and netaddr third-party libraries to find out the IPv6 prefix information for a given IPv6 address.

Make sure to have netifaces and netaddr installed in your system:

$ pip install netaddr 

The program is as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 3 
# This program is optimized for Python 2.7.12 and Python 3.5.2. 
# It may run on any other version with/without modifications. 
# This program depends on Python modules netifaces and netaddr. 
 
import socket 
import netifaces as ni 
import netaddr as na 
 
def extract_ipv6_info(): 
    """ Extracts IPv6 information""" 
    print ("IPv6 support built into Python: %s" %socket.has_ipv6) 
    for interface in ni.interfaces(): 
        all_addresses = ni.ifaddresses(interface) 
        print ("Interface %s:" %interface) 
        for family,addrs in all_addresses.items(): 
            fam_name = ni.address_families[family] 
 
            for addr in addrs: 
                if fam_name == 'AF_INET6': 
                    addr = addr['addr'] 
                    has_eth_string = addr.split("%eth") 
                    if has_eth_string: 
                        addr = addr.split("%eth")[0] 
                    try: 
                        print ("    IP Address: %s" 
                        %na.IPNetwork(addr)) 
                        print ("    IP Version: %s" 
                        %na.IPNetwork(addr).version) 
                        print ("    IP Prefix length: %s" 
                        %na.IPNetwork(addr).prefixlen) 
                        print ("    Network: %s" 
                        %na.IPNetwork(addr).network) 
                        print ("    Broadcast: %s" 
                        %na.IPNetwork(addr).broadcast) 
                    except Exception as e: 
                        print ("Skip Non-IPv6 Interface") 
 
if __name__ == '__main__': 
    extract_ipv6_info() 

The output from this script is as follows:

$ python 3_11_extract_ipv6_prefix.py 
IPv6 support built into Python: True
Interface lo:
    IP Address: ::1/128
    IP Version: 6
    IP Prefix length: 128
    Network: ::1
    Broadcast: ::1
Interface enp2s0:
    IP Address: 2001:6a8:308f:2:88bc:e3ec:ace4:3afb/128
    IP Version: 6
    IP Prefix length: 128
    Network: 2001:6a8:308f:2:88bc:e3ec:ace4:3afb
    Broadcast: 2001:6a8:308f:2:88bc:e3ec:ace4:3afb
    IP Address: 2001:6a8:308f:2:5bef:e3e6:82f8:8cca/128
    IP Version: 6
    IP Prefix length: 128
    Network: 2001:6a8:308f:2:5bef:e3e6:82f8:8cca
    Broadcast: 2001:6a8:308f:2:5bef:e3e6:82f8:8cca
Skip Non-IPv6 Interface
Interface wlp1s0: