请你解释一下下面这个类中的周长变量。
我知道
将周长定义为
这段代码来自一本书。
我知道
self.vertices
是指特定实例。由于perimeter
没有使用self
定义,这是否意味着它是一个类变量?那么它是否适用于所有实例?将周长定义为
self.perimeter
不是更好的方式吗?这样就可以适当地对每个实例进行声明了。这段代码来自一本书。
Polygon.py
import math
class Point:
def __init__(self, x, y):
self.x = x
self.y = y
def distance(self, p2):
return math.sqrt((self.x-p2.x)**2 + (self.y-p2.y)**2)
class Polygon:
def __init__(self):
self.vertices = []
def add_point(self, point):
self.vertices.append((point))
def perimeter(self):
perimeter = 0
points = self.vertices + [self.vertices[0]]
for i in range(len(self.vertices)):
perimeter += points[i].distance(points[i+1])
return perimeter
>>> square = Polygon()
>>> square.add_point(Point(1,1))
>>> square.add_point(Point(1,2))
>>> square.add_point(Point(2,2))
>>> square.add_point(Point(2,1))
>>> square.perimeter()
4.0
新类型
import math
class Point:
def __init__(self, x, y):
self.x = x
self.y = y
def distance(self, p2):
return math.sqrt((self.x-p2.x)**2 + (self.y-p2.y)**2)
class Polygon:
def __init__(self):
self.vertices = []
def add_point(self, point):
self.vertices.append((point))
def perimetermethod(self):
self.perimeter = 0
points = self.vertices + [self.vertices[0]]
for i in range(len(self.vertices)):
self.perimeter += points[i].distance(points[i+1])
return self.perimeter
if __name__=='__main__':
p1 = Polygon()
p1.add_point(Point(1,1))
p1.add_point(Point(1,2))
p1.add_point(Point(2,2))
p1.add_point(Point(2,1))
print(p1.perimetermethod())
square.perimeter
将获得 属性perimeter
而不是方法,然后使用square.perimeter()
调用它会导致错误。 - Ben