Python dynamic attribute creation

[Bruno Desthuilliers]

WANG Cong a écrit :
> 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.
> 
> My points are:
> 
(snip)

Python's classes are plain objects, and like any other object are 
created at runtime. Having to special-case them would break the 
simplicity and uniformity of Python for no good reason. Just like 
there's no good reason to make setattr() working differently for class 
and non-class objects.

FWIW, what you call "metaprogramming" is just ordinary programming - at 
least in Python. All your fears and concerns about Python's dynamism are 
just a priori learned from the "mainstream" B&D culture. From 
experience, these are non-issues - unless of course misused by some 
fool, but then there's no way to prevent stupids from doing stupid 
things. So, yes, Python rely quite a lot on programmer's common sense 
and discipline. Now the good news is that is JustWork(tm).