On 10/8/2014 9:09 PM, Terry Reedy wrote:
On 10/8/2014 6:57 AM, Steven D'Aprano wrote:
According to the documentation, operator.__add__ is the "official"
function,
and operator.add is just there for convenience.
You are paraphrasing "The function names are those used for special
class methods; variants without leading and trailing __ are also
provided for convenience." But then there is the following:
10.3.1. Mapping Operators to Functions
This table shows how abstract operations correspond to operator symbols
in the Python syntax and the functions in the operator module.
Operation Syntax Function
Addition a + b add(a, b)
etc, using the 'convenient' names. I would like to deprecate and
eventually remove the dunder names. To me, the duplication is not
'convenient'.
I'd be curious about a proposal to obsolete the double underscore
functions and just keep operator.add or to just keep the operator +
For me they seem rather distinct, though they are interchangable in
certain situations.
Perhaps I got something wrong, but all dunder functions are 'magic'
functions. Many of them mostly should ne used when when overloading
behaviour or when creating a class which should implement operators.
So for implemetation you use __add__ for using you use the operator +
if you need a
class MyClass(object):
def __init__(self, x, y):
self.x = x
self.y = y
# implements + for a certain type
def __add__(self, other):
return MyClass(self.x + other.x, self.y + other.y)
def __repr__(self):
return "(%f,%f)" % (self.x, self.y)
a = MyClass(1,2)
b = MyClass(4,5)
print(a)
print(b)
print(a+b)
# operator.add is identical to the + operator ,
# BUT it is a function and can thuss be
# assigned to variables passed as parameter
def dosomething(op, val1, val2):
return op(val1, val2)
print(dosomething(operator.add, 1, 2))
print(dosomething(operator.add, a, b))
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