python模拟post请求

Question

用原生urllib.request模拟post请求
from urllib import request, parse,error
import json
def get_page(url):

headers = {
    'User-Agent': 'Mozilla / 5.0(Windows NT 10.0;Win64;x64) AppleWebKit / 537.36(KHTML, likeGecko) Chrome / 66.0.3359.139Safari / 537.36',
    'Connection': 'keep-alive',
    "Referer": "http://test.m.youpenglai.cn/login",
    'Content-Type': 'application/json;charset=UTF-8',
    'Host':"test.m.youpenglai.cn"
}
data = {
    'loginname': '15057769636',
    'loginpassword': '123456',
    'logintype': '1'
}
# kets = "-"
# val = parse.quote(kets)
# url = url + val
data = parse.urlencode(data).encode('utf-8')
req = request.Request(url,data,headers,method='POST')
print(req)
try:
    page = request.urlopen(req).read()
    page = page.decode('utf-8')
    print(page)
    with open("./test.txt","wb+") as f:
        f.write(page)
except error.HTTPError as e:
    print(e.code())

return page

get_page('http://test.m.youpenglai.cn/y...')

错误提示是这个

urllib.error.HTTPError: HTTP Error 400: Bad Request