Post request returns empty string (python) - python-3.x

Question

I need to get data from site. To get this data user have to enter post code first. After exploring the source code i got the following.
Response result (that is what i need after all)
{PostCodePK: 16666, PostCode: "7468", City: "MACQUARIE HEADS", State: "TAS", Country: "AUST",…}
1
:
{PostCodePK: 16667, PostCode: "7468", City: "STRAHAN", State: "TAS", Country: "AUST",…}
Request Data.
Request URL:http://www.lucasmill.com/Resources/ws-common.aspx
Request Method:POST
Status Code:200 OK
Remote Address:111.67.1.113:80
Response Headers
view source
Cache-Control:private
Content-Length:321
Content-Type:application/json; charset=utf-8
Date:Tue, 21 Feb 2017 20:19:26 GMT
Expires:Tue, 21 Feb 2017 20:19:26 GMT
Server:Microsoft-IIS/8.5
Set-Cookie:dnn_IsMobile=False; path=/; HttpOnly
Request Headers
view source
Accept:application/json, text/javascript, */*; q=0.01
Accept-Encoding:gzip, deflate
Accept-Language:en-US,en;q=0.8,ru;q=0.6,uk;q=0.4
Connection:keep-alive
Content-Length:18
Content-Type:application/json; charset=UTF-8
Cookie:.ASPXANONYMOUS=ptTlH_jC0gEkAAAAZTU4MTA5NTItZmNlZS00MzRjLThmYTgtMWZkYWNkOTEwZmY00; dnn_IsMobile=False; language=en-AU; __utmt=1; __utma=97280258.254723646.1487697408.1487697408.1487708346.2; __utmb=97280258.1.10.1487708346; __utmc=97280258; __utmz=97280258.1487697408.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)
DNN-Service:true
DNN-Service-Method:GetTown
DNT:1
Host:www.lucasmill.com
Origin:http://www.lucasmill.com
Referer:http://www.lucasmill.com/Sawmilling-Contractors
User-Agent:Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36
X-Requested-With:XMLHttpRequest
Request Payload
{ 'param':'7468' }
Here is my python code.
import requests
r = requests.post('http://www.lucasmill.com/Resources/ws-common.aspx',data={ 'param':'7468' })
print(r.text)
but all i receive in response is an empty string.
Where am i wrong?

Answer 1

You need to add a few extra headers that particular application requires.
If you look at the request headers dump in the browser, you can see the following:
So, translated to python it will look like:
import json
import requests
headers = {
'DNN-Service': 'true',
'DNN-Service-Method': 'GetTown',
}
r = requests.post('http://www.lucasmill.com/Resources/ws-common.aspx',data=json.dumps({'param':7468}), headers=headers)
print(r.text)
Output:
[none][22:28:30] vlazarenko#alluminium (~/tests)$ python post.py
[{"PostCodePK":16666,"PostCode":"7468","City":"MACQUARIE
HEADS","State":"TAS","Country":"AUST","Latitude":"-42.2149353","Longitude":"145.1951436","CanGeocode":true},{"PostCodePK":16667,"PostCode":"7468","City":"STRAHAN","State":"TAS","Country":"AUST","Latitude":"-42.1534771","Longitude":"145.3281242","CanGeocode":true}]