from email.mime.multipart import MIMEMultipart
from email.mime.application import MIMEApplication
import requests

related = MIMEMultipart('form-data', '__-----------------------12774362691506035193370')
file_part = MIMEApplication(
    open('file', 'rb').read()
)
file_part.add_header('Content-disposition', 'attachment; name="name"; filename="filename"')
file_part.add_header('Content-Type', 'application/octet-stream')
related.attach(file_part)

body = related.as_string().split('\n\n', 1)[1]
headers = dict(related.items())
headers['User-Agent'] = 'user-agent'

url = 'url'
r = requests.post(url, data=body, headers=headers)
print(r.status_code)
print(r.text)