How can Tornado serve a single static file at an arbitrary location?

python tornado static-files
Randall Cook picture Randall Cook · Jan 21, 2014 · Viewed 9.7k times · Source

I am developing a simple web app with Tornado. It serves some dynamic files and some static ones. The dynamic ones are not a problem, but I am having trouble serving a static file. What I am looking to do is to serve the file /path/to/foo.json when the /foo.json URL is accessed.

Note that /path/to/foo.json is outside the document root. In Apache I would just set up an Alias. With Tornado I have:

app = tornado.web.Application([
    (r'/dynamic\.html', MyService, dict(param = 12345)),
    (r'/(foo\.json)', tornado.web.StaticFileHandler, {'path': '/path/to/foo.json'})
    ])

I added the regex group operator () to satisfy Tornado, which threw an exception otherwise. But now, when I access /foo.json, I get a 404: File Not Found.

Tests reveal that Tornado is attempting to use the path provided as a root directory to which it appends foo.json, implying my file could be found if it were at /path/to/foo.json/foo.json. Close, but not quite.

I suppose I could shorten my path to simply "/path/to", which will trigger a fetch of /path/to/foo.json upon the /foo.json URL, but this forces me to use the same name in the URL as on the filesystem. How can I just do a simple, arbitrary, URL to file mapping?

I have done some research on this, reading the documentation for tornado.web.Application and tornado.web.StaticFilehandler, plus some other SO questions. Nothing is quite my use case.

Answer

Mark picture Mark · Nov 30, 2014

StaticFileHandler expects two arguments, so if you want a single url (/foo.json) to be mapped to your file path you can use:

app = tornado.web.Application([
(r'/foo.json()', tornado.web.StaticFileHandler, {'path': '/path/to/foo.json'})
])

The regex will match /foo.json and send the empty capture group (), which will cause the filepath to be used as is. When the capture group is not empty, /path/to/foo.json will be treated as a directory /path/to/foo.json/, and the handler will try to match whatever is within the capture group to a file name in that directory.

Related questions

When to use Tornado, when to use Twisted / Cyclone / GEvent / other

Which of these frameworks / libraries would be the best choise for building modern multiuser web application? I would love to have an asynchronous webserver which will allow me to scale easly. What solution will give the best performance / scalability / most …

Read More
Tornado URL query parameters

I've been playing around with Tornado, and I've written some code that doesn't seem very nice. I'm writing an app to store recipes as an example. These are my handlers: handlers = [ (r"/recipes/", RecipeHandler), (r"/recipes", RecipeSearchHandler), #so query params …

Read More
How can I periodically execute a function with asyncio?

I'm migrating from tornado to asyncio, and I can't find the asyncio equivalent of tornado's PeriodicCallback. (A PeriodicCallback takes two arguments: the function to run and the number of milliseconds between calls.) Is there such an equivalent in asyncio? If …

Read More