import requests
from requests_toolbelt.multipart.encoder import MultipartEncoder

mp_encoder = MultipartEncoder(
    fields={
        'file': ('a.txt', open('a.txt', 'rb'), 'text/plain'),
        'file_type'      : 'text/plain',
        'id_specific'    : '23330'
    }
)

p_headers = {
  'Authorization': 'Bearer <valid token>',
  'Content-Type': mp_encoder.content_type
}

r= requests.put (
    'https://nyx.cz/api/file/upload',
    headers=p_headers,
    data=mp_encoder
)

print(r.text)

# {"error":true,"message":"422"}

body=get_mpart() # viz vyse
url="https://nyx.cz/api/file/upload"
#dat=urllib.parse.urlencode(body.('utf8'))
req = urllib.request.Request(url,data=body,method='PUT')
req.add_header('content-type' , 'multipart/form-data; boundary="' + boundary + '"')
req.add_header('content-length' , str(len(body)))
req.add_header('Authorization', 'Bearer ' + get_auth_token())
resp = request.urlopen(req).read()