This is a WSGI middleware that answers CORS preflight requests and adds the needed header to the response. For CORS see: http://www.w3.org/TR/cors/

Either plug it in programmatically as in this pyramid example:

def app(global_config, **settings):
    """ This function returns a WSGI application.

    It is usually called by the PasteDeploy framework during
    ``paster serve``.
    """

    def get_root(request):
        return {}

    config = Configurator(root_factory=get_root, settings=settings)
    config.begin()
    # whatever it takes to config your app goes here
    config.end()

    from wsgicors import CORS
    return CORS(config.make_wsgi_app(), headers="*", methods="*", maxage="180", origin="*")

or plug it into your wsgi pipeline via paste ini to let it serve by waitress for instance:

 [app:myapp]
 use = egg:mysuperapp#app

 ###
 # wsgi server configuration
 ###

 [server:main]
 use = egg:waitress#main
 host = 0.0.0.0
 port = 6543

 [pipeline:main]
 pipeline =
     cors
     myapp

 [filter:cors]
 use = egg:wsgicors#middleware
 # define a "free" policy
 free_origin=copy
 free_headers=*
 free_expose_headers=*
 free_methods=HEAD, OPTIONS, GET
 free_maxage=180

 # define a "subdom" policy
 subdom_origin=http://example.com http://example2.com https://*.example.com
 subdom_headers=*
 subdom_methods=HEAD, OPTIONS, GET, POST, PUT, DELETE
 subdom_expose_headers=Foo, Doom
 subdom_maxage=180

 # define a combination of policies, they are evaluated in the order given by the policy keyword
 # the first that matches the request's origin will be used
policy=subdom,free

Keywords are:

• origin
• headers
• methods
• credentials
• maxage

for origin:

• use copy which will copy whatever origin the request comes from
• a space separated list of hostnames - they can also contain wildcards like * or ? (fnmatch lib is used for matching). If a match is found the original host is returned.
• any other literal will be be copied verbatim (like * for instance to allow any source)

for headers:

• use * which will allow whatever header is asked for
• any other literal will be be copied verbatim

for expose_headers:

• use * to allow access to any header the client might wish to access
• any other literal will be be copied verbatim

for methods:

• use * which will allow whatever method is asked for
• any other literal will be be copied verbatim (like POST, PATCH, PUT, DELETE for instance)

for credentials:

• use true
• anything else will be ignored (that is no response header for Access-Control-Allow-Credentials is sent)

for maxage:

• give the number of seconds the answer can be used by a client, anything nonempty will be copied verbatim

As can be seen in the example above, a policy needs to be created with the policy keyword. The options need then be prefixed with the policy name and a _. The policy keyword itself can be a comma separated list. If so the origin of the request is matched against the origins defined in the policies and the first matching is the policy used.