Convert a field from string to ip type => need decimal?

Continuing the discussion from Convert a field from string to ip type:

"version" : {
"number" : "2.1.1",
"build_hash" : "40e2c53a6b6c2972b3d13846e450e66f4375bd71",
"build_timestamp" : "2015-12-15T13:05:55Z",
"build_snapshot" : false,
"lucene_version" : "5.3.1"

I was banging my head on this and I figured out that my template was set correctly however, I keep'd getting errors in logstash.log.

"_type"=>"logs", "_id"=>"AVJg2HO78OTigFwDifPm", "status"=>400, "error"=>{"type"=>"mapper_parsing_exception", "reason"=>"failed to parse [client_ip]", "caused_by"=>{"type"=>"number_format_exception", "reason"=>"For input string: """}}}}, :level=>:warn}

this was after enabling the type in the template:

"client_ip": {
"type": "ip",
"store": true

What I got is that an ip string was not wanted but a some other type. I converted it to decimal and it worked. I am not sure of the issue as I looked through (not an experienced java developer ):

Since client that is generating the logs is written in python I added this method to solve my problem. Not sure why string would through the error.

def ip2int(addr):
return struct.unpack("!I", socket.inet_aton(addr))[0]

Thanks in advance.