import urllib, urllib2, json
CHUNK_SIZE = 1024
url = "https://httpbin.org/post"

data = "*" * (1024 * 64 + 0)

req = urllib2.Request(url, data)
req.add_header("Content-Type", "application/text")
response = urllib2.urlopen(req)

res_data = []
while True:
    chunk = response.read(CHUNK_SIZE)
    res_data.append(chunk)
    if len(chunk) != CHUNK_SIZE:
        break
res_data = "".join(res_data)
response.close()

res = json.loads(res_data)

print len(res["data"])