On Aug 2, 5:51 am, Dave Angel <da...@ieee.org> wrote: > Simon wrote: > > Okay I will fix my code and include "self" and see what happens. I > > know I tried that before and got another error which I suspect was > > another newbie error. > > > The idea behind the init_Pre is that I can put custom code here to > > customize the __init__ instead of creating a new subclass. This kind > > of hook pattern allows you to flatten your inheritance hierarchy. I > > can choose in the init_Pre method to execute code before the init_exec > > (which contains the default __init__ code) and still execute the > > init_Exec method or I can completely customize the entire __init__ by > > returning False from init_Pre and prevent the init_Exec from being > > called. I use this type of pattern with almost all my methods. In > > this way I can create a less complicated inheritance chain but still > > have have custom code when needed without sub-classing. > > > I am use to Visual FoxPro which where you can do > > > =is.init_Pre().And.This.init_Exec() and the result is discarded so > > that is why it looks the way it does. In this form init_Exec has to > > return a value. However, If self.init_Pre(): self.init_Exec() would > > work the same and then I could avoid returning a value. > > > Thanks, > > Simon > > > On Aug 1, 5:52 am, Dave Angel <da...@ieee.org> wrote: > > >> Nat Williams wrote: > > >>> As MRAB described, ALL instance methods need to accept 'self' as a first > >>> parameter, as that will be passed to them implicitly when they are called. > >>> This includes __init__. The name 'self' is just a commonly accepted > >>> convention for the name of the instance object passed to methods. You > >>> don't > >>> have to call it that, but you really should. > > >>> Take a look athttp://docs.python.org/tutorial/classes.html#class-objects > >>> It might help shed some light on how methods and instances work. > > >>> One other thing. I'm a little confused by the first line of > >>> dcObject.__init__: > > >>> self.init_Pre() and self.init_Exec() > > >>> I suspect this does not do what you think it does. init_Pre and init_Exec > >>> will both be called by this expression (unless init_Pre throws an > >>> exception, > >>> of course). You're not getting anything here that you wouldn't by just > >>> calling each method on a separate line, except just making it harder to > >>> read. > > >> Read the doc-string for init_Pre() and for init_Exec(). The final > >> version of init_Pre() will return False in some circumstances, and in > >> those circumstances Simon doesn't want init_Exec() to be called. He's > >> deliberately using the short-circuit evaluation of 'and' to accomplish > >> that. > > >>> On Fri, Jul 31, 2009 at 8:53 PM, Simon <dciphercomput...@gmail.com> wrote: > > >>>> Hi > > >>>> So should the dcObject class include the "self" as well since I have > >>>> not defined an __init__ method in dcCursor? > > >>>> Simon > > >>>> -- > >>>>http://mail.python.org/mailman/listinfo/python-list > > >> Every one of those methods in both of those classes need a "self" first > >> argument. As others have said, all instance methods need a 'self.' > > (Please don't top-post. You should put new responses at the end of > quoted text, or sometimes inline if that's clearer.) > > I don't understand your comparison to Foxpro. read on. > > As your code was last posted, you don't need a return value from > init_Exec() Every function that doesn't have an explicit return will > return None. And None is interpreted as False in an "and" expression. > If you had an "if" around the whole thing, then you'd care. > > DaveA
All I meant by the FoxPro comment was the idea of using the equal sign without a variable to throw away the result. Also in FoxPro there is no such thing as automatically returning None. If there is no explicit return then True is returned. Thanks I did not know that None is interpreted as False. Simon -- http://mail.python.org/mailman/listinfo/python-list
