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[Python-Dev] Arbitrary attributes on funcs and methods
Guido van Rossumguido@python.org
Mon, 10 Apr 2000 12:02:36 -0400
> A number of people have played FAST and loose with function and method> docstrings, including John Aycock[1], Zope's ORB[2]. Docstrings are> handy because they are the one attribute on funcs and methods that are> easily writable. But as more people overload the semantics for> docstrings, we'll get collisions. I've had a number of discussions> with folks about adding attribute dictionaries to functions and> methods so that you can essentially add any attribute. Namespaces are> one honking great idea -- let's do more of those!>> Below is a very raw set of patches to add an attribute dictionary to> funcs and methods. It's only been minimally tested, but if y'all like> the idea, I'll clean it up, sanity check the memory management, and> post the changes topatches@python.org. Here's some things you can> do:>> -------------------- snip snip --------------------> Python 1.6a2 (#10, Apr 10 2000, 11:27:59) [GCC 2.8.1] on sunos5> Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam> >>> def a(): pass> ...> >>> a.publish = 1> >>> a.publish> 1> >>> a.__doc__> >>> a.__doc__ = 'a doc string'> >>> a.__doc__> 'a doc string'> >>> a.magic_string = a.__doc__> >>> a.magic_string> 'a doc string'> >>> dir(a)> ['__doc__', '__name__', 'func_code', 'func_defaults', 'func_dict', 'func_doc', 'func_globals', 'func_name', 'magic_string', 'publish']> >>> class F:> ... def a(self): pass> ...> >>> f = F()> >>> f.a.publish> Traceback (most recent call last):> File "<stdin>", line 1, in ?> AttributeError: publish> >>> f.a.publish = 1> >>> f.a.publish> 1Here I have a question. Should this really change F.a, or should itchange the method bound to f only? You implement the former, but I'mnot sure if those semantics are right -- if I have two instances, f1and f2, and you change f2.a.spam, I'd be surprised if f1.a.spam gotchanged as well (since f1.a and f2.a are *not* the same thing -- theyare not shared. f1.a.im_func and f2.a.im_func are the same thing, butf1.a and f2.a are distinct!I would suggest that you only allow setting attributes via the classor via a function. (This means that you must still implement thepass-through on method objects, but reject it if the method is boundto an instance.)--Guido van Rossum (home page:http://www.python.org/~guido/)
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