A simple python script for updating DNS zones using IPv6 and Dynv6's REST API

Dynv6.py

# Imports
import requests
import socket
import time
import traceback
import os

# Constants
ENDPOINT = "https://dynv6.com/api/update"
HOSTNAME = "....."
TOKEN = "......"
GOOGLE_IPv6_DNS = "2001:4860:4860::8888"

# Utility functions
def getPublicIpAddress():
    # Create a udp ipv6 socket and connects with Google's ipv6 primary dns server
    s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
    s.connect((GOOGLE_IPv6_DNS, 80))
    
    # Gets the socket ipv6
    ip = s.getsockname()[0]
    
    # Closes the socket
    s.close()
    print(f"Public IP: {ip}")
    return ip

def updateDynv6(ip):
    print(f"<- GET {ENDPOINT}?token={TOKEN}&hostname={HOSTNAME}&ipv6={ip}")
    
    # Updates the route via REST API
    response = requests.get(url=ENDPOINT, params={ 'token': TOKEN, 'hostname': HOSTNAME, 'ipv6': ip })

    print(f"-> {response.status_code} {ENDPOINT}")
    print(response.text)

	# Check whether the request was successful
    return response.status_code == 200

def fetchPublicIpCache():
	# Opens the cache.txt file, in order to not onerate the server by spamming requests and keeping track of the last ip request
	# even when the script restarts
    buffer = None

    with open("./cache.txt", "r") as fp:
        temp = fp.read()
        if temp != None and len(temp) > 0: buffer = temp

    return buffer

def updatePublicIpCache(ip):
	# Saves the new updated ip into the cache.txt file
    with open("./cache.txt", "w+") as fp:
        fp.write(str(ip))

def main():
    print("Starting dydns script...")

    # Create cache file if not exists
    if not os.path.exists("./cache.txt"):
        updatePublicIpCache("")

    # Get the current ip address
    last_ip_address = fetchPublicIpCache()
    print(f"Cached ip address: {last_ip_address}")

    while True:
        try:
            # Fetch the current ip address
            current_ip_address = getPublicIpAddress()

            # Detect whether it has changed and if the http request was successful
            if last_ip_address != current_ip_address and updateDynv6(current_ip_address):
				# Caches the new ip_address
                print("Caching ip address...")
                last_ip_address = current_ip_address
                updatePublicIpCache(current_ip_address)

			# Sleeps for two minutes before checking it again
            time.sleep(120)
        except:
			# In case of errors, print 'em and exit with status 1
            print(traceback.format_exc())
            exit(1)

main()

It's specially useful when using as a system service
Like specifying a systemd service to always restart it whenever it crashes

** requires python 3 **