Re: manipulating class attributes from a decorator while the class is being defined
Wilbert Berendsen a écrit : Hi, is it possible to manipulate class attributes from within a decorator while the class is being defined? I want to register methods with some additional values in a class attribute. But I can't get a decorator to change a class attribute while the class is still being defined. Something like: class Parser(object): regexps = [] def reg(regexp): def deco(func): regexps.append((regexp, func)) return func return deco @reg(r'.*') def quoted_string(self): pass How can I reach the class attribute `regexps' from within a decorator? Simple answer : you can't. Because, as you noticed, the class object doesn't exist yet. The canonical solutions are either to store regexps outside the class (ie: as a module level variable) - which can be problematic in some cases -, or to use a two-pass scheme using a decorator and a metaclass, where the decorator annotate the function with required informations for latter processing, and the metaclass do the effective processing. There are of course other solutions, some of them possibly simpler. The 'best' solution of course depends on intented use of your class... HTH -- http://mail.python.org/mailman/listinfo/python-list
Re: manipulating class attributes from a decorator while the class is being defined
Wilbert Berendsen [EMAIL PROTECTED] wrote: Hi, is it possible to manipulate class attributes from within a decorator while the class is being defined? I want to register methods with some additional values in a class attribute. But I can't get a decorator to change a class attribute while the class is still being defined. Something like: class Parser(object): regexps = [] def reg(regexp): def deco(func): regexps.append((regexp, func)) return func return deco @reg(r'.*') def quoted_string(self): pass How can I reach the class attribute `regexps' from within a decorator? Have you tried passing regexps into the decorator as a default argument? def reg(regexp, regexps=regexps): def deco(func): regexps.append((regexp, func)) return func return deco -- http://mail.python.org/mailman/listinfo/python-list
Re: manipulating class attributes from a decorator while the class is being defined
On Apr 19, 11:19 pm, Wilbert Berendsen [EMAIL PROTECTED] wrote: Hi, is it possible to manipulate class attributes from within a decorator while the class is being defined? I want to register methods with some additional values in a class attribute. But I can't get a decorator to change a class attribute while the class is still being defined. Something like: class Parser(object): regexps = [] def reg(regexp): def deco(func): regexps.append((regexp, func)) return func return deco @reg(r'.*') def quoted_string(self): pass How can I reach the class attribute `regexps' from within a decorator? Thanks for any help, Wilbert Berendsen --http://www.wilbertberendsen.nl/ You must be the change you wish to see in the world. -- Mahatma Gandhi --- def reg(regexp): def deco(func): def inner(self, *args, **kw): if not hasattr(self, 'regexps'): self.regexps = [] self.regexps.append((regexp, func)) return func(self, *args, **kw) return inner return deco class Parser(object): regexps = [] @reg(r'.*') def quoted_string(self): print 'hi' p = Parser() p.quoted_string() print p.regexps --- -- http://mail.python.org/mailman/listinfo/python-list
Re: manipulating class attributes from a decorator while the class is being defined
On Apr 19, 10:19 pm, Wilbert Berendsen [EMAIL PROTECTED] wrote: Hi, is it possible to manipulate class attributes from within a decorator while the class is being defined? I want to register methods with some additional values in a class attribute. But I can't get a decorator to change a class attribute while the class is still being defined. Something like: class Parser(object): regexps = [] def reg(regexp): def deco(func): regexps.append((regexp, func)) return func return deco @reg(r'.*') def quoted_string(self): pass How can I reach the class attribute `regexps' from within a decorator? In this particular example, it is enought to change the line def reg(regexp): to: def reg(regexp, regexps=regexps): So that 'regexps' inside reg() will point to the same object as 'regexps' outside reg(). Of course it wouldn't work well with inheritance, but it seems to me that you don't want to subclass 'Parser' anyway. If you did, you could instead have something like this: class Ruleset(list): def add(self, regexp): def decorator(func): self.append((regexp, func)) return func return decorator class Parser(object): rules = Ruleset() @rules.add(r'.*') def quoted_string(self): pass Or, yet another solution is to change the metaclass of 'Parser' so that it populates the class's rules by scanning its attributes. HTH -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
manipulating class attributes from a decorator while the class is being defined
Hi, is it possible to manipulate class attributes from within a decorator while the class is being defined? I want to register methods with some additional values in a class attribute. But I can't get a decorator to change a class attribute while the class is still being defined. Something like: class Parser(object): regexps = [] def reg(regexp): def deco(func): regexps.append((regexp, func)) return func return deco @reg(r'.*') def quoted_string(self): pass How can I reach the class attribute `regexps' from within a decorator? Thanks for any help, Wilbert Berendsen -- http://www.wilbertberendsen.nl/ You must be the change you wish to see in the world. -- Mahatma Gandhi -- http://mail.python.org/mailman/listinfo/python-list
Re: manipulating class attributes from a decorator while the class is being defined
Wilbert Berendsen schrieb: Hi, is it possible to manipulate class attributes from within a decorator while the class is being defined? I want to register methods with some additional values in a class attribute. But I can't get a decorator to change a class attribute while the class is still being defined. Something like: class Parser(object): regexps = [] def reg(regexp): def deco(func): regexps.append((regexp, func)) return func return deco @reg(r'.*') def quoted_string(self): pass How can I reach the class attribute `regexps' from within a decorator? It's really tricky . The class object doesn't exists yet. It's created after all functions are parsed and created. You have can walk up the stack frames but it's ugly. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: manipulating class attributes from a decorator while the class is being defined
How can I reach the class attribute `regexps' from within a decorator? Now, the first way that comes to my mind is simply overloading the class and set your regexps variable in your new class. The other way is to create an object and set it more manually (obj.regexps = ['.*']). Which for me is an ugly this to do because the first way is far more elegant :) -- GPG key: 0x04B3BB96 pgpqg8hSnWlWX.pgp Description: PGP signature -- http://mail.python.org/mailman/listinfo/python-list
