The following python script allows you to easily update the dynamic dns entry of a Namecheap domain using python and a cronjob.

dns_updater.py

import urllib2
import json
import xml.etree.ElementTree as Tree

# --------------------------------------------
from time import strftime, gmtime

host = "https://myexternalip.com/json"
# --------------------------------------------
dns_host = ""
dns_domain = ""
dns_key = ""


dns_request = "https://dynamicdns.park-your-domain.com/update?host="+dns_host+"&domain="+dns_domain+"&password="+dns_key+"&ip="


def get_online_ip():
    ip = urllib2.urlopen(host).read()
    data = json.loads(ip)
    return data.get('ip')


def get_saved_ip():
    try:
        with open("container-ip.tmp","r") as f:
            return f.read()
    except:
        save_ip("0.0.0.0")
        return "0.0.0.0"


def save_ip(ip):
    with open("container-ip.tmp","w+") as f:
        f.write(ip)
        pass


def request_change(ip):
    print("[X] - Challenge - New DNS Entry")
    result = urllib2.urlopen(dns_request+ip).read()
    tree = Tree.fromstring(result)
    res_com = tree.find('Command').text
    res_ip = tree.find('IP').text
    res_errors = tree.find('ErrCount').text
    res_done = tree.find('Done').text
    if (res_com == 'SETDNSHOST') and (res_ip == ip) and (res_errors == str(0)) and (res_done == 'true'):
        print("[X] - Challenge Successfull - DNS updated")
        save_ip(ip)
    else:
        print("[ ] - Challenge Failed - DNS not updated")
        print("[ --> "+result+" ]")
        ip_online = "0.0.0.0"
        save_ip(ip_online)


def timestamp_readable():
    return strftime("%Y-%m-%d %H:%M:%S", gmtime())


ip_current = get_saved_ip()
ip_online = get_online_ip()

print "{"+timestamp_readable()+"} DNS UPDATE SERVICE - [CURRENT:"+ip_current+"] [ONLINE: "+ip_online+"]"

if ip_current != ip_online:
    print "[X] - Requesting new IP: "+ip_online
    request_change(ip_online)
else:
    print "[ ] - Nothing changed"