The code on this page is not compatible with Python 3. 

https://www.zabbix.com/documentation/current/en/manual/appendix/protocols/header_datalen

packet = "ZBXD\1" + struct.pack('<Q', len(data)) + data

it fails with error:

TypeError: can only concatenate str (not "bytes") to str

 
Here is modified code line which works for v3:

packet = "ZBXD\1" + struct.pack('<Q', len(data)).decode() + data

i.e. we need to convert a middle part to string by calling method .decode() to it.

I verified result and it's correct. And it works with Python v2 too.