return response(environ, start_response)Here, environ is a dictionary containing all incoming information. The Request function
wraps all information in a manner that makes accessing the environ information a bit
more convenient. start_response is usually used to indicate the start of a response.
However, with Werkzeug you have the Response function, which takes care of the
response.
All parameters provided to the web service are found in the request.args attribute, and
this is what we provide to the get_option_value function. This function returns either an
error message in text form or the calculated option value in text form.
To be better able to serve this function (e.g., via a local web server), we put the function
into a separate WSGI script and add the serving functionality to it. Example 14-10 shows
the code of this script, called vol_pricing.py.
Example 14-10. Python script for volatility option valuation and web service helper
function
Valuation of European volatility options
in Gruenbichler-Longstaff (1996) model
square-root diffusion framework
— WSGI application for web service
from vol_pricing_service import get_option_value
from werkzeug.wrappers import Request, Response
from werkzeug.serving import run_simple
def application(environ, start_response):
request = Request(environ)
wrap environ in new object
text = get_option_value(request.args)
provide all parameters of call to function
get back either error message or option value
response = Response(text, mimetype=‘text/html’)
generate response object based on the returned text
return response(environ, start_response)
if name==‘main’:
run_simple(‘localhost’, 4000 , application)
Being in the right subdirectory (volservice), you can now start the application by
executing the following command via the shell or command-line interface:
$ python vol_pricing.py
* Running on http://localhost:4000/