Thx, really a nice and detailed explanation. On Tue, Mar 26, 2013 at 6:07 PM, Dave Angel <da...@davea.name> wrote:
> On 03/26/2013 02:17 AM, Shiyao Ma wrote: > >> Hi, >> suppose I have a file like this: >> class A: >> r = 5 >> def func(self, s): >> self.s = s >> a = A() >> print(a.r) # this should print 5, but where does py store the name of r >> >> a.func(3) >> print(a.s) # this should print 3, also where does py store this name. >> what's the underlying difference between the above example? >> >> > I don't think this is a scoping question at all. These references are > fully qualified, so scoping doesn't enter in. > > The class A has a dictionary containing the names of r and func. These > are class attributes. Each instance has a dictionary which will contain > the name s AFTER the A.func() is called. Ideally such an attribute will be > assigned in the __init__() method, in which case every instance will have s > in its dictionary. > > When you use a.qqq the attribute qqq is searched for in the instance > dictionary and, if not found, in the class dictionary. If still not found, > in the parent classes' dictionary(s). > > You can use dir(A) and dir(a) to look at these dictionaries, but it shows > you the combination of them, so it's not as clear. In other words, dir(a) > shows you both dictionaries, merged. (Seems to me dir also sometimes > censors some of the names, but that's a vague memory. It's never left out > anything I cared about, so maybe it's things like single-underscore names, > or maybe just a poor memory.) > > > -- > DaveA > -- > http://mail.python.org/**mailman/listinfo/python-list<http://mail.python.org/mailman/listinfo/python-list> > -- My gpg pubring is available via: gpg --keyserver subkeys.pgp.net--recv-keys 307CF736 More on: http://about.me/introom
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