[Python-ideas] Discourage operator.__dunder__ functions

[Guido van Rossum]

+1

On Apr 13, 2017 11:26 AM, "Steven D'Aprano" <steve at pearwood.info> wrote:

> Notice that I said *discourage* rather than *deprecate*.
>
> Quoting the documentation:
>
>     The operator module exports a set of efficient functions
>     corresponding to the intrinsic operators of Python. For
>     example, operator.add(x, y) is equivalent to the expression
>     x+y. The function names are those used for special class
>     methods; variants without leading and trailing __ are also
>     provided for convenience.
>
> https://docs.python.org/3/library/operator.html
>
> I propose four simple documentation changes, and no code change:
>
>
> (1) The quoted paragraph is factually wrong to say:
>
>     "The function names are those used for special class methods"
>
>     We can fix that by changing it to:
>
>     "Some function names are those used for special class methods".
>
>
> (2) Replace the word "convenience" in the quoted paragraph by
>     "backward compatibility";
>
>
> (3) Add a note close to the top of the page that the non-dunder
>     names are preferred for new code.
>
>
> (4) And a note stating that existing dunder functions will
>     remain, but no new ones will be added.
>
>
> The existing dunder names will remain aliases to the non-dunder names;
> they will not be deprecated (maybe in Python 5000 *wink*). Those who
> really want to use them can continue to do so.
>
> Regarding point (1) above:
>
> - Not all operator functions have a dunder alias.
>
> - The dunder functions don't always correspond to a dunder method. For
> example, there is operator.__concat__ for sequence concatenation, but no
> str.__concat__ or list.__concat__ methods.
>
> - Even when the dunder function corresponds by name to the dunder
> method, they don't mean the same thing. For example, operator.__add__ is
> *not* the same as just calling the first argument's __add__ method.
>
> - And finally, I fail to see how having to type an extra four characters
> is a "convenience".
>
>
> Long ago, when the operator module was first introduced, there was a
> much stronger correspondence between the operator.__dunder__ functions
> and dunder methods. But I think that correspondence is now so weak that
> we should simply treat it as a historical artifact.
>
>
>
> --
> Steve
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