Performing file upload post request

Question

I am trying to upload a file to a server, using python. The API of the server has to accept the file, together with some other parameters.

This is why i open the file, and then i create a dictionary, containing the file and the other parameters that the web app accepts, and then encode it and perform a POST request with the item.

This is the code:

from urllib import request
from urllib.parse import urlencode
import json
with open('README.md', 'rb') as f:
 upload_credentials = {
 "file": f,
 "descr": "testing",
 "title": "READMEE.md",
 "contentType": "text",
 "editor": username,
 }
 url_for_upload = "" #here you place the upload URL
 
 req = request.Request(url_for_upload, method="POST")
 form_data = urlencode(upload_credentials)
 form_data = form_data.encode()
 
 response = request.urlopen(req, data=form_data)
 http_status_code = response.getcode()
 content = response.read()
 print(http_status_code)
 print(content)

However, i get an error in this line: response = request.urlopen(req, data=form_data) The server responds with a 500 HTTP Status Code.

This is what i get as an error message:

raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 500:

500 error codes can mean a lot of things and i do not know how to progress any further, as everything i did seems by the book...

Does anyone have the experience, given the info provided here, to guide me to some potential solution?

EDIT: I am trying to replicate working js code that does the same thing. This is it:

<input type="file" />
<button onclick="upload()">Upload data</button>
<script>
 upload = async() =>
 { 
 const fileField = document.querySelector('input[type="file"]');
 await uploadDoc(fileField.files[0] );
 };
 
 uploadDoc = async( file ) =>
 { 
 let fd = new FormData();
 fd.append( 'file', file ); 
 fd.append( 'descr', 'demo_upload' );
 fd.append( 'title', name );
 fd.append( 'contentType', 'text' );
 fd.append( 'editor', user );
 let resp = await fetch( url, { method: 'POST', mode: 'cors', body: fd }); 
 };
</script>

• Chris Doyle: What value should file have in the dict? the contents of the file? cause right now it just has the file handle reference.
• Patrick Artner: are you trying to stream the file? you add the filehandle to your "upload_credentials"
• S P Sharan: Could you provide the docs to the API you are using?
• mrxra: shouldn't "file": f rather be "file": f.read() ?
• user1584421: @SPSharan The server accepts a POST request to a particular url. You can see in the updated question an example of the form that it accepts.

Answer 1

The js code is doing a multipart/form-data post request.
I do not believe urllib supports multipart/form-data, you can use request instead.

import requests 
with open('README.md', 'rb') as f:
 files = {"file": f}
 upload_credentials = {
 "descr": "testing",
 "title": "READMEE.md",
 "contentType": "text",
 "editor": username,
 }
 r = requests.post("http://httpbin.org/post", files=files, data=upload_credentials) 
 print(r.status_code)
 print(r.text)

• user1584421: Thank you very much! So the trick was that this was a multipart form POST request. Thanks again!