import requests
import json
url = 'https://www.mywbsite.fr/Services/GetFromDataBaseVersionned'
payload = {'Host': 'www.mywbsite.fr', 'Connection': 'keep-alive',
    'Content-Length': 129, 'Origin': 'https://www.mywbsite.fr',
    'X-Requested-With': 'XMLHttpRequest', 'User-Agent':
    'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.52 Safari/536.5'
    , 'Content-Type': 'application/json', 'Accept': '*/*', 'Referer':
    'https://www.mywbsite.fr/data/mult.aspx', 'Accept-Encoding':
    'gzip,deflate,sdch', 'Accept-Language':
    'fr-FR,fr;q=0.8,en-US;q=0.6,en;q=0.4', 'Accept-Charset':
    'ISO-8859-1,utf-8;q=0.7,*;q=0.3', 'Cookie':
    'ASP.NET_SessionId=j1r1b2a2v2w245; GSFV=FirstVisit=; GSRef=https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CHgQFjAA&url=https://www.mywbsite.fr/&ei=FZq_T4abNcak0QWZ0vnWCg&usg=AFQjCNHq90dwj5RiEfr1Pw; HelpRotatorCookie=HelpLayerWasSeen=0; NSC_GSPOUGS!TTM=ffffffff09f4f58455e445a4a423660; GS=Site=frfr; __utma=1.219229010.1337956889.1337956889.1337958824.2; __utmb=1.1.10.1337958824; __utmc=1; __utmz=1.1337956889.1.1.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=(not%20provided)'
    }
headers = {}
r = requests.post(url, data=json.dumps(payload), headers=headers)
print(r.content)
python send POST with header