Method returns self?

[Gerhard Häring]

On Thu, Oct 18, 2001 at 11:36:46PM -0400, Ignacio Vazquez-Abrams wrote:
> On Thu, 18 Oct 2001, Roy Smith wrote:
> 
> > I've got a data file parser that returns a data object.  You call it
> > something like this:
> >
> > parser = myParser()
> > data = parser.parse(filename)
> >
> > Now, I want to give the data class a verify() method.  The parser only
> > ensures that the data file has a parsable syntax, but there are also a
> > number of higher-level semantic checks that we might want to do.  I have in
> > mind something that you would call like this:
> >
> > parser = myParser()
> > try:
> >    data = parser.parse(filename).verify()
> > except data.VerifyError:
> >    print "you bozo"
> >
> > The idea is that verify() is a method of the data class which either
> > returns self, or raises an exception.  The code would look something like:
> >
> > class data:
> >    def verify (self):
> >       if everthing is cool:
> >          return self
> >       else:
> >          raise VerifyError
> >
> > My question is, will I run into garbage collection or reference count
> > problems if a method returns self?  I can't quite put my finger on it, but
> > I have this vague feeling I might end up with a self-referential object.

You should only be getting refcount problems when you have circular
references, like that:

def foo():
  x = {}; y = {}; x[1] = y; y[1] = x

x and y are referencing each other and normally won't be collected when
foo() returns. But they will be if you build your Python with
"--with-cycle-gc". I don't know if this option is already activated by
default.

As Ignacio already said, in your case there are no circular references.

Gerhard
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