Hi,
I am working on a project (nevow + twisted) where lots of statistical computing is done using "R", interfaced by rpy.py. It works very well. To be able to parameterize the computing, I defined an additional namespace and put the parameters with this namespace inside the nevow templates. It looks like:
<html xmlns:nevow="http://nevow.com/ns/nevow/0.1"
xmlns:new_namespace="http://new_namespace.de/ns/0.1"
xmlns="http://www.w3.org/1999/xhtml"
xml:lang="de" lang="de">
<head>
<meta content="text/html; charset=ISO-8859-1" http-equiv="content-type" />
</head>
<body>
<img
new_namespace:title="Fehlerklasse 2 (letzte 50)"
new_namespace:table="defect"
new_namespace:fields="measurement_id gravity"
new_namespace:reorder_x="1"
new_namespace:reverse_x="1"
new_namespace:sql="class = 2 ORDER BY _id DESC LIMIT 50"
new_namespace:function="errorplot"
new_namespace:smooth="2"
nevow:data="Measurement"
nevow:render="Plot">
</body>
</html>
The parameters are extracted like this:
def data_Measurement (self, context, data):
"""Extracts the parameters from the attribute-list.".
self.html_params = {}
self.script_params = None
todelete = []
for theKey in context.tag.attributes:
keyFound = False
if type(theKey) is tuple:
if len(theKey) == 2:
ns = theKey[0]
tag = theKey[1]
if ns == u'http:// new_namespace.de/ns/0.1' :
name = tag
value = context.tag.attributes.get(theKey)
self.script_params[name] = value
##
## Append the key to the list of keys to remove later.
## Unfortunately the parameters must be cleared, so that only valid attributes
## according the html-element are present in the rendering step.
##
todelete.append(theKey)
##
## Delete the param-keys from the attribule-list.
## Otherwise the attributes would be present in the rendering and this is for the birds.
##
for theKey in todelete:
del context.tag.attributes[theKey]
In the function render_measurement() the function is called with the parameters (in this case "errorplot") and the resulting image is rendered. This also works very well. My question is: Is there a better and simpler way to do that? And if not, why do I have to remove the additional attributes, because later on nevow gets confused about this attributes and produces a nice stack-trace?
The next question is: In the render_whatever() functions an image is produced, and I want to write the image directly with perhaps request.write(). How can this be done using nevow?
Thanks,
Werner
participants (1)
-
Stumpe, Werner