Python Requests: Post JSON and file in single request

Don't encode using json.

import requests

info = {
    'var1' : 'this',
    'var2'  : 'that',
}

data = {
    'token' : auth_token,
    'info'  : info,
}

headers = {'Content-type': 'multipart/form-data'}

files = {'document': open('file_name.pdf', 'rb')}

r = requests.post(url, files=files, data=data, headers=headers)

Note that this may not necessarily be what you want, as it will become another form-data section.

See this thread How to send JSON as part of multipart POST-request

Do not set the Content-type header yourself, leave that to pyrequests to generate

def send_request():
    payload = {"param_1": "value_1", "param_2": "value_2"}
    files = {
        'json': (None, json.dumps(payload), 'application/json'),
        'file': (os.path.basename(file), open(file, 'rb'), 'application/octet-stream')
    }

    r = requests.post(url, files=files)
    print(r.content)