Content-Type: multipart/form-data; boundary=${bound} 

import os, random, sys, requests
from requests_toolbelt.multipart.encoder import MultipartEncoder

url = 'http://127.0.0.1/sendmsg'
argvstr = sys.argv[1:]
argv_dict = {}
for argv in argvstr :
 argv = str(argv).replace("\r\n" , "")
 DICT = eval(argv)
 argv_dict.update(DICT)

headers = {
 'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:50.0) Gecko/20100101 Firefox/50.0',
 'Referer': url
 }

multipart_encoder = MultipartEncoder(
 fields={
  'username': argv_dict['username'],
  'pwd': argv_dict['pwd'],
  'type': 'txt',
  'friendfield': argv_dict['friendfield'],
  'friend': argv_dict['friend'],
  'content': argv_dict['content'],
  'file': (os.path.basename(argv_dict['file']) , open(argv_dict['file'], 'rb'), 'application/octet-stream')
  #file为路径
  },
  boundary='-----------------------------' + str(random.randint(1e28, 1e29 - 1))
 )

headers['Content-Type'] = multipart_encoder.content_type
#请求头必须包含一个特殊的头信息，类似于Content-Type: multipart/form-data; boundary=${bound}

r = requests.post(url, data=multipart_encoder, headers=headers)
print(r.text)
#注意，不要设置cookies等其他参数，否则会报错

# 例子/usr/local/python36/bin/python3 /opt/lykchat/test_upload.py "{'username':'lykchat','pwd':'123456','type':'img','friendfield':'1','friend':'xxxx','content':'恭喜发财','file':'/root/b.jpg'}"
#等同于curl -F "file=@/root/a" 'http://127.0.0.1/sendmsg?username=lykchat&pwd=123456&type=img&friendfield=1&friend=xxxx&content=恭喜发财'