Flask: How to handle application/octet-stream

Question

I want to make a multiple file-upload form.I use jQuery File Uploader. My server-side code:

@app.route("/new/photogallery",methods=["POST"])
def newPhotoGallery():
    print request.files

I tried two things:

Submit form normally:

When i submit my form normally,it prints:

ImmutableMultiDict([('post_photo_gallery', FileStorage: u'' ('application/octet-stream'))])
Submit form using AJAX:

When i submit my form using AJAX,it prints:

ImmutableMultiDict([])

My first question is: Why is there a difference between AJAX request and normal request.
My second question is: How can i handle this application/octet-streamrequest in Flask/Python My third question is: Is this a good way to use application/octet-stream ?

By the way i do not know much about application/octet-stream.Thank you very much.

If you're on Chrome, look at the Network tab of the developer tools and see what the two requests look like. — Blender
– Blender, Commented Apr 12, 2013 at 22:16
------WebKitFormBoundaryxInpKfVFK8mUuqOv Content-Disposition: form-data; name="post_photo_gallery"; filename="" Content-Type: application/octet-stream lines are dont appeared on the AJAX request — saidozcan
– saidozcan, Commented Apr 12, 2013 at 22:20
This might be useful: github.com/blueimp/jQuery-File-Upload/wiki/Flask — Blender
– Blender, Commented Apr 12, 2013 at 22:22
when i data_file = request.files.get('data_file') print this one it prints None, i changed 'data_file' with name of my input in the form :( — saidozcan
– saidozcan, Commented Apr 12, 2013 at 22:26

Yibo Yang · Accepted Answer · 2018-03-13 06:10:20Z

3

Regardless of the the data encoding, you should be able to get the raw data with request.data. In the case of application/octet-stream, you can just write request.data to a binary file.

An example handler for various data types:

from flask import json

@app.route('/messages', methods = ['POST'])
def api_message():

    if request.headers['Content-Type'] == 'text/plain':
        return "Text Message: " + request.data

    elif request.headers['Content-Type'] == 'application/json':
        return "JSON Message: " + json.dumps(request.json)

    elif request.headers['Content-Type'] == 'application/octet-stream':
        with open('/tmp/binary', 'wb') as f:
            f.write(request.data)
            f.close()
        return "Binary message written!"

    else:
        return "415 Unsupported Media Type ;)"

The typical scenario of handling form data is already documented here.

answered Mar 13, 2018 at 6:10

Yibo Yang

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3 Comments

markmnl Over a year ago

that didn't work for me when sending application/octet-stream, I get:

File "...\lib\site-packages\werkzeug\test.py", line 884, in run_wsgi_app     app_rv = app(environ, start_response) TypeError: 'int' object is not callable

8.8.8.8 Over a year ago

@markmnl You can use request.stream.read as shown in izmailoff.github.io/web/flask-file-streaming

steff_bdh Over a year ago

when using multipart/form-data or application/x-www-form-urlencoded to send files, flask stores the file comes in request.files as shown here flask.palletsprojects.com/en/1.1.x/patterns/fileuploads

dalethestirling · Accepted Answer · 2013-07-14 10:17:08Z

I was unable to get a request working using application/octet-stream type posts, but have used multipart/form-data type forms in the past to upload images using flask.

I have extended what I have done in the past to support multiple upload files and this has worked leveraging werkzeug's FileStorage objects.

The key here is setting up a post based route that is looking for a request element from a form. This should allow you to POST to the route either via a standard form or an AJAX call.

Below is a simplified example that is using a form:

Template for the view:

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>jQuery File Upload Example</title>
</head>
<body>
{% if err %}
    <h4>{{ err }}</h4>
{% endif %}

<form action="/" method=POST enctype=multipart/form-data id="fileupload">
    <input type="file" name="files" data-url="/" multiple>
    <input type=submit value=Post>
</form>

{% if files %}
{% for file in files %}
<p>Uploaded: <b>{{ file }}</b> </p>
{% endfor %}
{% endif %}
</body> 
</html>

Flask App

from flask import Flask, request, render_template
from werkzeug import secure_filename, FileStorage
import os

# Flask functions
app = Flask(__name__) 
app.config.from_object(__name__)
DEBUG = True 
# add this so that flask doesn't swallow error messages
app.config['PROPAGATE_EXCEPTIONS'] = True

@app.route('/', methods=['GET', 'POST'])
def uploader():
    if request.method =='POST' and request.files.getlist('files'):
        up_file_list = []

        # Iterate the through a list of files from the form input field
        for a_file in request.files.getlist('files'):
            if a_file.filename:
                # Validate that what we have been supplied with is infact a file
                if not isinstance(a_file, FileStorage):
                    raise TypeError("storage must be a werkzeug.FileStorage")
                # Sanitise the filename
                a_file_name = secure_filename(a_file.filename)
                # Build target
                a_file_target = os.path.join('/tmp/', a_file_name)
                # Save file 
                a_file.save(a_file_target)
                up_file_list.append(a_file_name)
        # Return template
        if up_file_list:
            return render_template('uploader.html', err=None, files=up_file_list)
        else:
            return render_template('uploader.html', err='No Files Uploaded', files=None)
    else:
        return render_template('uploader.html', err=None, files=None) 


# application execution 
if __name__ == '__main__': 
    app.run()

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