python as-lookup

from pysnmp.hlapi import *
from prtg.sensor.result import CustomSensorResult
from prtg.sensor.units import ValueUnit
import sys
import re
import json

prtg_params = json.loads(sys.argv[1])


def bgp_peer_walk(host):
  oid = '.1.3.6.1.2.1.15.3.1.2'
  reg_ex = re.compile('[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+ = [1-6]')
  bgp_peer_dict = {}

  for (errorIndication,
   errorStatus,
   errorIndex,
   varBinds) in nextCmd(SnmpEngine(), 
                        CommunityData(prtg_params['snmpcommv2']),
                        UdpTransportTarget((host, 161)),
                        ContextData(),                                                           
                        ObjectType(ObjectIdentity(oid)),
                        lexicographicMode=False):
    if errorIndication:
      csr = CustomSensorResult(text="Python Script pysnmp error")
      csr.error = f"Python Script pysnmp error: {errorIndication}"
      print(csr.json_result)
      sys.exit()
    elif errorStatus:
      csr = CustomSensorResult(text="Python Script pysnmp error")
      csr.error = f"Python Script pysnmp error: {errorStatus}"
      print(csr.json_result)            
      sys.exit()
    else:
      for varBind in varBinds:
        bgp_peers = reg_ex.search(str(varBind))
        ip, state = str(bgp_peers.group(0)).split(' = ')
        bgp_peer_dict[ip] = state
  return(bgp_peer_dict)

def build_csr(peer_dict):
  try:
    csr = CustomSensorResult()
    for peer in peer_dict:
      if peer_dict[peer] is '6':
        csr.add_channel(name = peer, value = 6, unit = ValueUnit.CUSTOM, is_warning = 0, value_lookup="customsensor.bgp4.peerstatus")
      if peer_dict[peer] is '5':
        csr.add_channel(name = peer, value = 5, unit = ValueUnit.CUSTOM, is_warning = 1, value_lookup="customsensor.bgp4.peerstatus")
      if peer_dict[peer] is '4':
        csr.add_channel(name = peer, value = 4, unit = ValueUnit.CUSTOM, is_warning = 1, value_lookup="customsensor.bgp4.peerstatus")
      if peer_dict[peer] is '3':
        csr.add_channel(name = peer, value = 3, unit = ValueUnit.CUSTOM, is_warning = 1, value_lookup="customsensor.bgp4.peerstatus")
      if peer_dict[peer] is '2':
        csr.add_channel(name = peer, value = 2, unit = ValueUnit.CUSTOM, is_warning = 1, value_lookup="customsensor.bgp4.peerstatus")
      if peer_dict[peer] is '1':
        csr.add_channel(name = peer, value = 1, unit = ValueUnit.CUSTOM, is_warning = 1, value_lookup="customsensor.bgp4.peerstatus")
    print(csr.json_result)
  except Exception as e:
    csr = CustomSensorResult(text="Python build_csr execution error")
    csr.error = f"Python Script execution error: {e}"
    print(csr.json_result)

build_csr(bgp_peer_walk(prtg_params['host']))

Here is what the above code is Doing:
1. The prtg_params variable is a dictionary that contains the parameters passed to the script by PRTG.
2. The bgp_peer_walk function is a function that uses the pysnmp library to walk the BGP4-MIB::bgpPeerState OID.
3. The build_csr function is a function that builds the CustomSensorResult object.
4. The build_csr function is called with the bgp_peer_walk function as the argument.
5. The build_csr function loops through the dictionary returned by the bgp_peer_walk function and adds a channel for each BGP peer.
6. The build_csr function prints the CustomSensorResult object as JSON.
7. PRTG parses the JSON and displays the results.