Thank you Alan, Dave and Cameron (and folks managing this email group)! Your replies were very helpful.
Regards ni On Wed, Apr 9, 2014 at 4:25 AM, Cameron Simpson <c...@zip.com.au> wrote: > On 08Apr2014 22:58, Ni hung <niih...@gmail.com> wrote: > > I am learning programming using python. I think of solving a problem > using > > functions and for this reason all/most of my code consists of functions > and > > no classes. I have some understanding of classes/Object Oriented > > Programming. I can write simple classes but I do not understand when to > use > > classes. > > Loosely speaking, you can usefully make a class when there is a > particular type of object on which you are make an assortedment of > operations. > > For example, if you have several functions looking like this: > > def modify_thing1(obj1, ...): > > def add_something(obj1, ...): > > and so on, where obj1 is always the same kind of thing, representing > some well define idea you have when writing the code. > > In that circumstance you might make a class looking like this: > > class ObjName(object): > > def __init__(self): > # "self" here is an "obj1" as used above > # set whatever attributes an "obj1" should have to start with > # you can pass in some of those values as parameters to the __init__ > function > > def modify(self, ...): > # this is the same as "modify_thing1(obj1, ...)" earlier > # using "self" as "obj1" > > def add(self, ...): > # this is the same as "add_something(obj1, ...)" earlier > > Then your code looks like: > > obj1 = ObjName() > ... > obj1.modify(5) > obj1.add(6) > > or what have you. > > This has several advantages: > > - all the code that affects this kind of object is in one place > > - you can remove all the specifics of how things are done from the main > code and keep them inside the class methods. > This makes the main code more readable (if you pick good method names) > and shorter (also more readable, usually). > > - later, if need be, you can change the inner workings of how > ObjNames work without changing the main code, or at least not > much - sometimes not at all > > Anyway, that's an ok rule of thumb for when to make a class: when > you have a bunch of operations to do to one type of thing. > > Cheers, > -- > Cameron Simpson <c...@zip.com.au> > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor >
_______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
