Receiving large files with @tornado.web.stream_request_body

Nagy László Zsolt gandalf at
Wed Sep 24 14:37:37 CEST 2014

I was using tornado 3 before. I see that file streaming was included in 
version 4. This is something I need for posting large files.

I have a problem receiving multiple files with a single POST request. 
Client side could be something like this:

<form action="/postfiles">
   First file: <input type="file" name="fname1"><br>
   Second file: <input type="file" name="fname2"><br>
Third file: <input type="file" name="fname3"><br>
<input type="submit" value="Submit">

Suppose the user has seleted 3 large ISO files, I would like to stream 
them into files on the server side. This is what I was trying:

class PostFilesHandler(tornado.web.RequestHandler):
     def post(self):
         for postfile in self.request.files:
                 print("File info:",postfile) # There is no 
postfile["body"] here!!!

     def prepare(self):
         self.temp_file = tempfile.NamedTemporaryFile(delete=False)

     def data_received(self, chunk):
         self.temp_file.write(chunk) # This is great but which file is 

The problem is obvious: the data_received method receives raw data, but 
how do I tell when data body for a file ends and another begins? How can 
I save the body of all posted files into different named temp files, and 
then access them from from the post() method?

The main reason for using  this is to limit memory usage. Some files 
might be GB sized and I don't want to store them in memory. Can please 
someone point me to a working example?



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