Nested Function Question

[Ian Kelly]

On Fri, Jan 6, 2012 at 2:46 PM, GZ <zyzhu2000 at gmail.com> wrote:
> Hi,
>
> I am reading the documentation of functools.partial (http://
> docs.python.org/library/functools.html#functools.partial) and found
> the following 'reference implementation' of functools.partial.
>
> def partial(func, *args, **keywords):
>    def newfunc(*fargs, **fkeywords):
>        newkeywords = keywords.copy()
>        newkeywords.update(fkeywords)
>        return func(*(args + fargs), **newkeywords)
>    newfunc.func = func
>    newfunc.args = args
>    newfunc.keywords = keywords
>    return newfunc
>
> I don't understand why the below 3 lines are needed:
>
>    newfunc.func = func
>    newfunc.args = args
>    newfunc.keywords = keywords
>
>
> It is as if they are trying to prevent garbage collection, but I don't
> get why it is needed. As long as something holds reference to newfunc,
> because it in turn references keywords and args, nothing will be
> freed. If nothing is referencing newfunc, then everything should be
> freed.

They exist for introspection.  The partial object has to store the
function and arguments it was passed so that it can call it later, so
as long as they're being stored anyway, why not make them visible?