Uploading CSV to Flask for background processing

Question

I'm looking to use Flask to host a single-page website that would allow users to upload a CSV that would be parsed and put into a database. All of the database shenanigans are complete (through SQLalchemy in another Python script) and I've got everything worked out once a script has access to the CSV, I just need help getting it there.

Here's the scenario:

1. User directs browser at URL (probably something like 
   http://xxx.xxx.xxx.xxx/upload/)
2. User chooses CSV to upload
3. User presses upload
4. File is uploaded and processed, but user is sent to a thank you page while our
   script is still working on the CSV (so that their disconnect doesn't cause the
   script to abort).

It's totally cool if the CSV is left on the server (in fact, it's probably preferred since we'd have a backup in case processing went awry)

I think what I want is a daemon that listens on a socket, but I'm not really experienced with this and don't know where to start getting it configured or setting up Flask.

If you think some framework other than Flask would be easier, definitely let me know, I'm not tied to Flask, I've just read that it's pretty easy to set up!

Thank you very much!!

Answer 1

Here is a (very slightly simplified) example of handling file uploading in web.py based on a cook book example (the Flash example, which I have less experience with, looks even easier):

import web

urls = ('/', 'Upload')

class Upload:
    def GET(self):
        web.header("Content-Type","text/html; charset=utf-8")
        return """
               <form method="POST" enctype="multipart/form-data" action="">
               <input type="file" name="myfile" />
               <br/>
               <input type="submit" />
               """

    def POST(self):
        x = web.input(myfile={})
        filedir = '/uploads' # change this to the directory you want to store the file in.
        if 'myfile' in x: # to check if the file-object is created
            filepath=x.myfile.filename.replace('\\','/') # replaces the windows-style slashes with linux ones.
            filename=filepath.split('/')[-1] # splits the and chooses the last part (the filename with extension)
            fout = open(filedir +'/'+ filename,'wb') # creates the file where the uploaded file should be stored
            fout.write(x.myfile.file.read()) # writes the uploaded file to the newly created file.
            fout.close() # closes the file, upload complete.
        raise web.seeother('/')

if __name__ == "__main__":
   app = web.application(urls, globals()) 
   app.run()

This renders a upload form, and then (on POST) reads the uploaded file and saves it to a designated path.