How to receive uploaded file with Klein like Flask in python

Question

When setting up a Flask server, we can try to receive the file user uploaded by

imagefile = flask.request.files['imagefile']
filename_ = str(datetime.datetime.now()).replace(' ', '_') + \
    werkzeug.secure_filename(imagefile.filename)
filename = os.path.join(UPLOAD_FOLDER, filename_)
imagefile.save(filename)
logging.info('Saving to %s.', filename)
image = exifutil.open_oriented_im(filename)

When I am looking at the Klein documentation, I've seen http://klein.readthedocs.io/en/latest/examples/staticfiles.html, however this seems like providing file from the webservice instead of receiving a file that's been uploaded to the web service. If I want to let my Klein server able to receive an abc.jpg and save it in the file system, is there any documentation that can guide me towards that objective?

Answer 1

As Liam Kelly commented, the snippets from this post should work. Using cgi.FieldStorage makes it possible to easily send file metadata without explicitly sending it. A Klein/Twisted approach would look something like this:

from cgi import FieldStorage
from klein import Klein
from werkzeug import secure_filename

app = Klein()

@app.route('/')
def formpage(request):
    return '''
    <form action="/images" enctype="multipart/form-data" method="post">
    <p>
        Please specify a file, or a set of files:<br>
        <input type="file" name="datafile" size="40">
    </p>
    <div>
        <input type="submit" value="Send">
    </div>
    </form>
    '''

@app.route('/images', methods=['POST'])
def processImages(request):
    method = request.method.decode('utf-8').upper()
    content_type = request.getHeader('content-type')

    img = FieldStorage(
        fp = request.content,
        headers = request.getAllHeaders(),
        environ = {'REQUEST_METHOD': method, 'CONTENT_TYPE': content_type})
    name = secure_filename(img[b'datafile'].filename)

    with open(name, 'wb') as fileOutput:
        # fileOutput.write(img['datafile'].value)
        fileOutput.write(request.args[b'datafile'][0])

app.run('localhost', 8000)

For whatever reason, my Python 3.4 (Ubuntu 14.04) version of cgi.FieldStorage doesn't return the correct results. I tested this on Python 2.7.11 and it works fine. With that being said, you could also collect the filename and other metadata on the frontend and send them in an ajax call to klein. This way you won't have to do too much processing on the backend (which is usually a good thing). Alternatively, you could figure out how to use the utilities provided by werkzeug. The functions werkzeug.secure_filename and request.files (ie. FileStorage) aren't particularly difficult to implement or recreate.