On 11/10/2012 2:33 PM, Jennie wrote:
What is the best solution to solve the following problem in Python 3.3?
import math
>>> 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=Point()):
... """Return the distance from `point`."""
... return math.sqrt((self - point).x ** 2 + (self - point).y ** 2)
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 5, in Point
NameError: name 'Point' is not defined
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)
...
>>> p = Point()
>>> p.distance()
0.0
>>> p.distance(Point(3, 4))
5.0
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
The second 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=Point()):
... return math.sqrt((self - point).x ** 2 + (self - point).y ** 2)
...
>>> Point.distance = distance
>>> p = Point()
>>> p.distance(Point(3, 4))
5.0
my first thought
The last one:
>>> class Point:
... def __init__(self, x=0, y=0):
... self.x = x
... self.y = y
... Point.distance = distance
... def __sub__(self, other):
... return Point(self.x - other.x, self.y - other.y)
...
>>> def distance(self, point=Point()):
... return math.sqrt((self - point).x ** 2 + (self - point).y ** 2)
...
>>> p = Point()
>>> p.distance(Point(3, 4))
5.0
Is there a better solution?
--
Terry Jan Reedy
--
http://mail.python.org/mailman/listinfo/python-list
