On 06/26/10 03:31, Carl Banks <pavlovevide...@gmail.com> wrote: > On Jun 25, 6:15 am, WANG Cong <xiyou.wangc...@gmail.com> wrote: >> Hi, list! >> >> I have a doubt about the design of dynamic attribute creation by >> assignments in Python. >> >> As we know, in Python, we are able to create a new attribute of >> a class dynamically by an assignment: >> >> >> >> >>> class test: pass >> ... >> >>> test.a = "hello" >> >>> test.a >> 'hello' >> >> However, I still don't get the points why Python designs it like this. > [snip points] > > > I understand you and think your proposal is reasonable. I know a few > people who use Python who would agree with you, and even go farther. > > You did well to propose not banning attributes per se, but making it > harder to set them. Python isn't really in the business of making > questionable things impossible (there are occasions where it does, > like killing threads), but it is in the business of making things that > are questionable enough harder. What you propose is reasonable under > Python's design principles (provided that initializer functions were > exempted), and if Python had been designed as you propose, I don't > think it would have suffered that much. >
Thanks much for encouraging me! This makes me feeling less guilty. ;-) > Here's the thing: Python doesn't consider creating dynamic attributes > to be questionable. Python doesn't merely allow for dynamicism, it > encourages it. And encouraging something means to make it simple. > Understand, but please consider my proposal again, if we switched to: setattr(foo, 'new_attr', "blah") by default, isn't Python still dynamic as it is? (Please teach me if I am wrong here.) This why I said the questionable thing is not so much related with dynamic programming or not. > I know you won't agree with this, and I'm not trying to convince you > or argue with you. I'm just telling you why it's like that. > > I will also tell you that claims like "it's doesn't use good OOP > principles" or "C++ does it that way" carry almost no credit. How C++ > does something is a suggestion, nothing more. > In fact I wanted to avoid comparing Python with C++. :) When I talked about OOP, it is general OOP, not related with any concrete programming languages. -- Live like a child, think like the god. -- http://mail.python.org/mailman/listinfo/python-list
