William Purcell wrote: > I am writing a application to calculate pressure drop for a piping > network. Namely a building sprinkler system. This will be a > command line program at first with the system described in xml (at > least that is how I think I want to do it). > > An important part of this calculation is finding the 'hydraulically > most remote' sprinkler. This is something that I could specify with > an attribute for now and later think about how to automate it. I > need to walk through the dom tree until I find a node of type > "sprinkler" that has an attribute of hydraulically_most_remote with > a value of True. > > After I find this I need to break the itterator/for loop and then > start walking backwards keeping a running total of the pressure drop > until I reach a node that has multiple pipesections and then walk to > the end of each branch and calculate the pressure drop, and then add > them to the branch that contained the hydraulically most remote > sprinkler, and then move on, repeating this until I walk all the way > back to the inflow node. > > I am having trouble finding a decent python/xml resource on the web. > I have ordered Python & XML by Jones and Drake, but I am anxious to > get something started. The only decent online resource that I can > seem to find is > > http://pyxml.sourceforge.net/topics/howto/xml-howto.html > > which doesn't seem to be a very comprehensive how-to. > > Do demonstrate just about everything I know about xml and python I > attached t.py and ex.xml. > > Another thing that is confusing is dir(walker) does not show walker > having an attribute currentNode and dir(walker.currentNode) does not > show walker.currentNode having an attribute tagName.
I'd probably start with a few python classes representing the sprinkler system. The exact layout may change a few times until you have found one that makes your questions clear and the calculations as easy as possible. You can then add a read_model_from_file() function converting the xml into your model using ElementTree or its close relative lxml. My guess is that it'll be a lot more fun this way... Peter -- http://mail.python.org/mailman/listinfo/python-list
