from urllib import request, parse

url="https://aip.baidubce.com/rpc/2.0/kg/v1/cognitive/entity_annotation?access_token=24.a8f6ce5dd84a6b57f15495321eddb8de.2592000.1546307549.282335-14937033"
data={'data':'百万美元宝贝的评价'}
header={"content-type": "application/json"}

data=parse.urlencode(data).encode("utf-8")
req=request.Request(url=url, headers=header, data=data)

page=request.urlopen(req).read().decode("utf-8")

print(page)

错误：{"log_id": 3829852863518939746, "error_code": 282003, "error_msg": "missing parameters: data"}