What use is '__reduce__'?

[Ian Kelly]

As you found by searching, __reduce__ is used to determine how
instances of the class are pickled. If the example you're using
doesn't do any pickling, then it's not really relevant to the example.
It's probably included so that it won't be missed when the code is
copied.

On Fri, Jan 8, 2016 at 9:42 AM, Robert <rxjwg98 at gmail.com> wrote:
> Hi,
>
> When I try to run the following code:
>
>
>
> /////
> from collections import Counter, OrderedDict
>
> class OrderedCounter(Counter, OrderedDict):
>      'Counter that remembers the order elements are first seen'
>      def __repr__(self):
>          return '%s(%r)' % (self.__class__.__name__,
>                             OrderedDict(self))
>      def __reduce__(self):
>          return self.__class__, (OrderedDict(self),)
>
> oc = OrderedCounter('abracadabra')
> -----
>
> I don't know the use of '__reduce__', even I look it up on Python website.
> On that website, it explains 'pickle' module:
> https://docs.python.org/2/library/pickle.html
>
> But the above example without import that module. Is it from built-in?
> Anyhow, I don't find a built-in explanation about '__reduce__'.
>
> What use of the above two new self methods are in class OrderedCounter?
>
> Thanks,
>
>
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