方法1：
import requests
url = "http://www.xxxx.net/login"
#参数拼凑,附件上传格式如picurl参数，其他表单参数值拼成tuple格式：
2-tuples (filename, fileobj),
3-tuples (filename, fileobj, contentype)，
4-tuples (filename, fileobj, contentype, custom_headers)
files = {"username": (None, "billy"), "password": (None, "abcd1234"),
'pi
