[C++-sig] C++ chain method works unexpectedly in Python

[Charles Solar]

Ahh very cool, exactly what I was looking for.
I did not know about __builtin__._  Figured it was something funny like
that, glad its just a shell thing.
Thank you

On Sun, Apr 17, 2011 at 9:07 PM, INADA Naoki <songofacandy at gmail.com> wrote:

> Python Interactive shell stores result of an expression to a variable
> named '__builtin__._'.
> So, ``del _`` may help you.
>
> This behavior is only on interactive shell. When running script, '_'
> is not used and Python
> may acts you expect.
>
>
> On Mon, Apr 18, 2011 at 9:56 AM, Charles Solar <charlessolar at gmail.com>
> wrote:
> > I have a python module written in C++, and the C++ code has a few
> instances
> > that involve method chaining.  I was experimenting with python support
> for
> > these methods and I found something odd.
> > However it seems this is more a python eccentricity than Boost Python,
> > consider the following code sample.
> >
> > class Test():
> >     def __init__( self ):
> >             print "Init"
> >     def __del__( self ):
> >             print "Del"
> >     def foo( self ):
> >             print "Foo"
> >             return self
> >     def bar( self ):
> >             print "Bar"
> >             return self
> >
> > And some sample uses:
> >
> >>> Test().foo().bar()
> > Init
> > Foo
> > Bar
> > <__main__.Test instance at 0x2aef40e33998>
> >>>
> >
> > Note that __del__ was never called, the object still exists somewhere..
> > There is another odd thing though, if I repeat the same line, the
> previous
> > version gets destroyed and replaced by the new version, but only after
> the
> > chain methods are done, eg:
> >
> >>>> Test().foo().bar()
> > Init
> > Foo
> > Bar
> > Del                      <-- Old one, NOT the current instance
> > <__main__.Test instance at 0x2b72bc78d998>
> >>>
> >
> > However if I do:
> >
> > def Tester():
> >     Test().foo().bar()
> >     # To make sure del is not called by the function returning
> >     while True:
> >             pass
> >
> >>> Tester()
> > Init
> > Foo
> > Bar
> > Del
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> >   File "<stdin>", line 4, in Tester
> > KeyboardInterrupt
> >>>
> >
> > That time __del__ was called immediately ( as intended ).
> >
> > Is there something I should be aware of here?  Some sort of difference
> > between the global instances and ones defined in a function?  Can I do
> > anything so global instances are cleaned up immediately like they are
> inside
> > functions?
> >
> > Thanks
> >
> >
> >
> > _______________________________________________
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> >
>
>
>
> --
> INADA Naoki  <songofacandy at gmail.com>
> _______________________________________________
> Cplusplus-sig mailing list
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