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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: operator module functions
Date: Wed, 08 Oct 2014 02:28:57 -0400
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On 10/7/2014 9:41 PM, Steven D'Aprano wrote:
> Every Python operator has a function version in the operator module:
>
> operator + has function operator.add;
> operator - has function operator.sub;
> operator * has function operator.mul;
>
> and so forth. Only, that's not quite right... according to the
> documentation, the "official" functions are actually:
>
> operator.__add__;
> operator.__sub__;
> operator.__mul__;
>
> etc., with the underscore-less versions being provided as a convenience.
>
> Was anyone aware of this?

Of course. It has bugged me a bit for years.  Messy.

> Is there anyone who uses or prefers the dunder versions?

I don't and don't, and that seems to be true of other core devs: there 
are no non-test uses of the dunder methods in the stdlib.  Grepping 
/lib/*.py recursively for 'operator.' gives 540 hits, most for 
operator.someop.  Grepping the same for 'operator.__' returns 4 hits for 
operator.__name__ and .__doc__ (not operators) and these 6 tests:

C:\Programs\Python34\Lib\test\test_richcmp.py: 88:     "lt": (lambda 
a,b: a< b, operator.lt, operator.__lt__),
C:\Programs\Python34\Lib\test\test_richcmp.py: 89:     "le": (lambda 
a,b: a<=b, operator.le, operator.__le__),
C:\Programs\Python34\Lib\test\test_richcmp.py: 90:     "eq": (lambda 
a,b: a==b, operator.eq, operator.__eq__),
C:\Programs\Python34\Lib\test\test_richcmp.py: 91:     "ne": (lambda 
a,b: a!=b, operator.ne, operator.__ne__),
C:\Programs\Python34\Lib\test\test_richcmp.py: 92:     "gt": (lambda 
a,b: a> b, operator.gt, operator.__gt__),
C:\Programs\Python34\Lib\test\test_richcmp.py: 93:     "ge": (lambda 
a,b: a>=b, operator.ge, operator.__ge_

If there a back-compatibility excuse?  I cannot remember what operator 
had in 1.4 or whenever it was added, if after that.

-- 
Terry Jan Reedy