Hi Keshav, On 2012-05-03, Keshav Kini <keshav.k...@gmail.com> wrote: > Simon King <simon.k...@uni-jena.de> writes: >> No idea. Clearly, unless there is a good reason, the init method of the >> base class should be called at some point. But I was not aware of a >> convention whether the base init should be called first or last or >> whatever. Does someone have a pointer? > > I think the reasoning behind calling the parent class's initializer > before the child class's initializer is that the parent class doesn't > know about the child class, so the parent class shouldn't be expected to > successfully initialize something that has already been modified by the > child class. On the other hand, the child class does know about its > parent classes and can be designed to handle the result of whatever > initialization the parent class has done.
I figured that the argument for an initialisation that is anti-parallel to the mro would be like that. Some special initialisation steps would, for example, expect that self.variable_names() is present, which is only available *after* calling Ring.__init__. On the other hand: One could argue that the parent class can expect that some basic tools (such as __hash__ and __repr__) already work when being called. Hence, before calling __init__ of the parent class, one is supposed to make sure that the "tool chain" is provided. And one could argue that a commutative algebra is, in the *first* place, a commutative algebra, then in the *second* place it is an algebra, which is a module and a commutative ring (which then is a ring), which are parents. From that point of view, one would expect that the initialisation goes from the most specific to the most general - hence, *parallel* to the mro. I simply don't know if there is any convention established (by that I mean: Documented, and I'd like to see a link) among Python developers, or at least among Sage developers. Best regards, Simon -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
