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Re: Method default argument whose type is the class not yet defined

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On 11/10/2012 09:29 PM, Terry Reedy wrote:

> On 11/10/2012 2:33 PM, Jennie wrote:
>>
>> I propose three solutions. The first one:
>>
>>  >>> class Point:
>> ...     def __init__(self, x=0, y=0):
>> ...         self.x = x
>> ...         self.y = y
>> ...     def __sub__(self, other):
>> ...         return Point(self.x - other.x, self.y - other.y)
>> ...     def distance(self, point=None):
>> ...         p = point if point else Point()
>> ...         return math.sqrt((self - p).x ** 2 + (self - p).y ** 2)

> What I do not like about this one is that it creates a new 0 point each
> time one is needed. Two solutions:
>
> change Point() to point0 in the distance function and create
> point0 = Point()
> after the class.
>
> -or-
> instead of p = line,
> px,py = point.x, point.y if point else 0.0, 0.0

Thanks, I like the second one :)

-- 
Jennie

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Method default argument whose type is the class not yet defined Jennie <nameDOTportua@gmail.com> - 2012-11-10 20:33 +0100
  Re: Method default argument whose type is the class not yet defined Chris Angelico <rosuav@gmail.com> - 2012-11-11 06:56 +1100
  Re: Method default argument whose type is the class not yet defined Terry Reedy <tjreedy@udel.edu> - 2012-11-10 15:29 -0500
    Re: Method default argument whose type is the class not yet defined Jennie <nameDOTportua@gmail.com> - 2012-11-10 21:51 +0100
      Re: Method default argument whose type is the class not yet defined Dave Angel <d@davea.name> - 2012-11-10 17:30 -0500
    Re: Method default argument whose type is the class not yet defined Jennie <marco.buttu@gmail.com> - 2012-11-10 21:51 +0100
  Re: Method default argument whose type is the class not yet defined Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-11 01:13 +0000
    Re: Method default argument whose type is the class not yet defined Chris Angelico <rosuav@gmail.com> - 2012-11-11 13:13 +1100
    Re: Method default argument whose type is the class not yet defined Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-10 19:43 -0700
      Re: Method default argument whose type is the class not yet defined Roy Smith <roy@panix.com> - 2012-11-10 21:53 -0500
        Re: Method default argument whose type is the class not yet defined Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-10 23:43 -0700
        Re: Method default argument whose type is the class not yet defined Ian Kelly <ian.g.kelly@gmail.com> - 2012-11-10 23:45 -0700
    Re: Method default argument whose type is the class not yet defined Chris Angelico <rosuav@gmail.com> - 2012-11-11 13:47 +1100
    Re: Method default argument whose type is the class not yet defined Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-11 14:21 +0000
      Re: Method default argument whose type is the class not yet defined Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-11 22:31 +0000
        Re: Method default argument whose type is the class not yet defined Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-12 00:31 +0000
          Re: Method default argument whose type is the class not yet defined Steve Howell <showell30@yahoo.com> - 2012-11-11 16:56 -0800
          Re: Method default argument whose type is the class not yet defined Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-12 04:46 +0000
        Re: Method default argument whose type is the class not yet defined Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-11-12 01:10 +0000
          Re: Method default argument whose type is the class not yet defined Roy Smith <roy@panix.com> - 2012-11-11 20:15 -0500
            Re: Method default argument whose type is the class not yet defined Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-11-12 01:35 +0000
        Re: Method default argument whose type is the class not yet defined Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-12 01:18 +0000
          Re: Method default argument whose type is the class not yet defined Roy Smith <roy@panix.com> - 2012-11-11 20:34 -0500
        Re: Method default argument whose type is the class not yet defined Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-11-12 01:29 +0000
        Re: Method default argument whose type is the class not yet defined Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-12 01:50 +0000
  Re: Method default argument whose type is the class not yet defined Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-11 01:23 +0000
  Re: Method default argument whose type is the class not yet defined Steve Howell <showell30@yahoo.com> - 2012-11-11 16:32 -0800

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