Question #97842 on DOLFIN changed: https://answers.launchpad.net/dolfin/+question/97842
Anders Logg proposed the following answer: On Mon, Jan 18, 2010 at 10:23:54AM -0800, Johan Hake wrote: > On Monday 18 January 2010 08:29:03 dbeacham wrote: > > New question #97842 on DOLFIN: > > https://answers.launchpad.net/dolfin/+question/97842 > > > > Is there a less hacked way to add extra parameter values to be used in an > > Expression in python than: > > > > class MyExp(Expression): > > def __new__(cls, *args, **kwargs): > > obj = Expression.__new__(cls, **kwargs) > > return obj > > > > def __init__(self, *args): > > .... > > .... > > It has been possible to pass user defined optional arguments to the __init__ > method. But it looks like a regression has kicked in. > > I have fixed the regression in dolfin dev, and added a doc string example. > > You should now be able to do: > > class MyExp(Expression): > def __init__(self, **kwargs): > self._mesh = kwargs['mesh'] > self._domain = kwargs['domain'] > def eval(self, values, x): > info(self._mesh, 1) > info(self._domain, 1) > > mesh = UnitCube(1,1,1) > domain = MeshFunction("uint", mesh, 0) > e = MyExp(mesh=mesh, domain=domain) > e(0,0,0) > > Do not use *args and do _not_ call the base class __init__. Yes, it is counter > intuitive but it is a result of having the Expression class do both compiled > Expressions and python derived Expressions. > > I prefer having two classes, CompiledExpression and Expression, so we could > say goodbye to this kind of troubles ;) I'd prefer keeping "Expression" for the simplest option which is visible in most demos: f = Expression("sin(x[0])") and find a suitable name for Expression with eval. Ideally, it should also be the same in C++. Candidates are UserExpression ComplexExpression But I'm not sure I like any of them. -- Anders > Johan > > > > where *args are my extra parameters (ie mesh, mesh functions etc.) and > > __new__ might have to be better worked if I had included my own kwargs. > > The above seems to work ok, but let me know of any major problems with it. > > > > I could always use a MyExp.init(...) function after I've created an > > instance to set up class variables, but just curious as to whether I > > missed something obvious for a one line initiation. > > > > David. > > > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : [email protected] > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp -- You received this question notification because you are a member of DOLFIN Team, which is an answer contact for DOLFIN. _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
