Steven Bethard wrote:John M. Gabriele wrote: class C(object): @classmethod def f(cls, *args): # do stuff
Sorry -- I'm not as far along as you suspect. :) I've never yet seen this "@classmethod" syntax. I'm supposing that it's part of this so-called "new-style" class syntax.
This is syntactic sugar in Python 2.4 for:
class C(object):
def f(cls, *args):
# do stuff
f = classmethod(f)So if you'd like to check the docs, look in the builtins for classmethod (and staticmethod):
http://docs.python.org/lib/built-in-funcs.html
From your reply, I gather that, unless I'm using this special syntax (@classmethod or @staticmethod), all my def's are supposed to take 'self' as their first arg.
Yup. You're of course welcome to name it whatever you like, but the methods defined in your class (when not wrapped with classmethod, staticmethod, etc.) will all be called with an instance of the class as their first argument. So you need to make sure 'self' or something like it is the first parameter to the function.
So then, are all def's -- that take 'self' as their first -- argument -- in a class statement, instance methods?
Basically, yes. (Again, assuming they're not wrapped with anything.)
Consider the difference between str.join and ''.join:
py> str.join <method 'join' of 'str' objects>>
py> ', '.join <built-in method join of str object at 0x01233620>>
Hmm... weird.
Ok, the point here is that str.join and ', '.join are not the same object. The reason is that, when the ', ' instance of str is created, new "bound method" objects are created for each of the instance methods in str. These "bound methods" all know that the first argument to their functions is ', '.
[snip]py> ', '.join(['a', 'b', 'c']) 'a, b, c'
Check.
py> str.join(', ', ['a', 'b', 'c']) 'a, b, c'
What's happening here?
str.join is the "unbound method" of the str object. So just like you have to declare 'self' as the first argument of all your instance methods, the writer of the str object methods also declared 'self' as the first argumetn to str.join. So str.join looks something like:
class str(object):
...
def join(self, sequence):
...So when you access it like str.join(...) you should be passing it an instance and a sequence. On the other hand, the "bound method" created for ', ' has already bound the instance, so it no longer expects the 'self' argument to be passed in.
HTH,
STeVe -- http://mail.python.org/mailman/listinfo/python-list
