Large file upload in Flask

I am attempting to implement a flask application for uploading files. This file could be very large. For example, almost 2G in size.

I have finished the server side process function like this:

@app.route("/upload/<filename>", methods=["POST", "PUT"])
def upload_process(filename):
    filename = secure_filename(filename)
    fileFullPath = os.path.join(application.config['UPLOAD_FOLDER'], filename)
    with open(fileFullPath, "wb") as f:
        chunk_size = 4096
        while True:
            chunk = flask.request.stream.read(chunk_size)
            if len(chunk) == 0:
                return

            f.write(chunk)
    return jsonify({'filename': filename})

As for browser side, I should give users a from to submit the file. One file at a time. Show progressbar to indicate the uploading process. But I have no idea about the browser side code. How can I use javascript code to start the uploading and show it status?

This will be a difficult task for your to figure out on your own. I would suggest a plugin like https://blueimp.github.io/jQuery-File-Upload/

You can see from this projects source code they use a method name which essentially looks at how large the file is and how much data has been transferred thus far and how much remains to show a percentage complete div.

code example from this project

progressall: function (e, data) {
                var $this = $(this);
                $this.find('.fileupload-progress')
                    .find('.progress').progressbar(
                        'option',
                        'value',
                        parseInt(data.loaded / data.total * 100, 10)
                    ).end()
                    .find('.progress-extended').each(function () {
                        $(this).html(
                            ($this.data('blueimp-fileupload') ||
                                    $this.data('fileupload'))
                                ._renderExtendedProgress(data)
                        );
                    });
            }

https://github.com/blueimp/jQuery-File-Upload/blob/master/js/jquery.fileupload-jquery-ui.js

So if you do want to come up with your own solution, I would suggest you start by building a UI div rectangle which has a dynamic width which updates according to your percentage calculation based upon the file upload size and data uploaded... or just go with an already established solution.