On 08/08/17 02:22, boB Stepp wrote: > "@staticmethod" then there are two ways of calling the method, using > objects or using the class. Is there some reason not to use the > "ClassName.a_static_method()" syntax? Are there intended uses for > doing this?
classes are objects too... You could have a list of objects, some of which are classes and some instances. Its nice to use polymorphism and just call the staticmethod (or classmethod) and let the interpreter do the hard work without having to test types - a nasty non-OO style of programming that should be avoided if possible > Class methods look to be something I will find difficult to find a use for. Once you start using objects a lot they come in very useful. I don't think I've built any significant OO system without using at least a few class methods. Remember that class methods conceptually act on the class as a whole - ie on all instances both current and future. So any time you have a large group of objects and you want to set some kind of state for all of them you can use classmethods to set class state. Instance methods can refer to the class state and modify their behaviour accordingly. (Some OO gurus argue that you should only set class state via a class method, although you can do it via an instance too - but what if you need to set it when no instances exist. In Python direct access allows that from outside the class, but in other OO systems you need a class method.) Class methods are also the best place to put alternate constructors - eg loading from a database given an instance ID or by parsing a string representation. Class methods can also be used to manage caches of instances, do global searches of instances (eg from a database) etc. >> (1) There are very, very few good uses for static methods in Python. If >> you think you need a static method, you probably could just use a >> regular module-level function. Amen to that, I try to avoid staticmethods... and so far have never found a valid use for one. I treat them as a piece of legacy from earlier versions, prior to classmethods. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
