[Web-SIG] WSGI Open Space @ PyCon.

[P.J. Eby]

At 03:43 PM 3/30/2009 +0300, Sergey Schetinin wrote:
>Did you consider a variation that eliminates the start_response but
>returns status and headers as first item of the iterable? Considering
>how response is usually generated it could save some code in some
>cases and wouldn't add any overhead in others, it also has a pleasant
>similarity to the HTTP response format:
>
>   def simple_app(environ):
>       """Simplest possible application object"""
>       status = '200 OK'
>       response_headers = [('Content-type','text/plain')]
>       yield status, response_headers
>       yield 'Hello world!\n'


I thought about this, and also a variant where status is in the 
headers, as a 'Status' header ala CGI, with a default of '200 
OK'.  In which case, the following would both be valid apps:

     def simple_app(environ):
         return [('Content-type','text/plain')], "Hello world!\n"

     def simple_app(environ):
         yield [('Content-type','text/plain')]
         yield "Hello world!\n"

However, the main reason I suggested the fixed 3-tuple return is to 
*discourage* the use of generators as response bodies, because a lot 
of people think that they should use yield to build up the output, 
ala 'print' in CGI.  This is really bad for performance, given that 
iterator yielding is supposed to be used to flush the output channel.

Unless you're transmitting a large file, you really should just be 
returning one string with the entire body in the common case.  As you 
point out, it's not that difficult to wrap something with a decorator 
to use one of these simple styles if you need to.