Irv Kalb wrote: > I have been writing OOP code for many years in other languages and for the > past few years in Python. I am writing new curriculum for a course on OOP > in Python. In order to see how others are explaining OOP concepts, I have > been reading as many books and watching as many videos as I can. I've > been watching some videos created by Dr. Chuck Severance in a series > called "Python For Everyone". I think "Dr. Chuck" is an excellent teacher > and I think his videos are outstanding. > > Today I watched this video: https://www.youtube.com/watch?v=b2vc5uzUfoE > <https://www.youtube.com/watch?v=b2vc5uzUfoE> which is about 10 minutes > long. In that video he gives a very basic overview of OOP and classes. > He gives a demonstration using the following example: > > class PartyAnimal(): > x = 0 > > def party(self): > self.x = self.x + 1 > print('So far', self.x) > > an = PartyAnimal() > an.party() > an.party() > an.party()
This style is rather brittle. Consider the following variant: >>> class A: ... x = "" ... >>> a = A() >>> b = A() >>> a.x += "a" >>> a.x += "a" >>> b.x += "b" >>> a.x 'aa' >>> b.x 'b' >>> A.x '' Seems to work. Now let's change x to something mutable: >>> A.x = [] >>> a = A() >>> b = A() >>> a.x += "a" >>> a.x += "a" >>> b.x += "b" >>> a.x ['a', 'a', 'b'] >>> b.x ['a', 'a', 'b'] >>> A.x ['a', 'a', 'b'] Conclusion: don't do this except to learn how attributes work in Python. -- https://mail.python.org/mailman/listinfo/python-list
