# coding: utf-8
class
geometricobject:
def__init__
(self, color = "green", filled = "true"):
self.__color = color
self.__filled = filled
defgetcolor
(self):
return self.__color
defsetcolor
(self, color):
self.__color = color
defisfilled
(self):
return self.__filled
defsetfilled
(self, filled):
self.__filled = filled
def__str__
(self):
return
"color: " + self.__color + \
" and filled: " + str(self.__filled)
# coding: utf-8
from geometricobject import geometricobject
import math
class
circle
(geometricobject):
def__init__
(self, radius):
geometricobject.__init__(self)
self.__radius = radius
defgetradius
(self):
return self.__radius
defsetradius
(self, radius):
self.__radius = radius
defgetarea
(self):
return self.__radius * self.__radius * math.pi
defgetdiameter
(self):
return
2 * self.__radius
defgetperimeter
(self):
return
2 * self.__radius * math.pi
defprintcircle
(self):
print self.__str__() + "radius: " + str(self.__radius)
# override the __str__() method defined in geometricobject
def__str__
(self):
return geometricobject.__str__(self) + " radius: " + str(self.__radius)
from geometricobject import geometricobject
class
rectangle
(geometricobject):
def__init__
(self, width = 1, height = 2):
geometricobject.__init__(self)
self.__width = width
self.__height = height
defgetwidth
(self):
return self.__width
defsetwidth
(self, width):
self.__width = width
defgetheight
(self, height):
return self.__height
defsetheight
(self, height):
self.__height = height
defgetarea
(self):
return self.__width * self.__height
defgetperimeter
(self):
return
2 * (self.__width + self.__height)
# override the __str__ method defined in geometricobject
def__str__
(self):
return geometricobject.__str__(self) + " width: " + \
str(self.__width) + " height: " + str(self.__height)
# coding: utf-8
from circlefromgeometricobject import circle
from rectanglefromgeometricobject import rectangle
defmain
():# display circle and rectangle properties
c = circle(4)
r = rectangle(1, 3)
displayobject(c)
displayobject(r)
print
"are the circle and rectangle the same size? " , \
issamearea(c, r)
# display geometric object properties
defdisplayobject
(g):
print g.__str__()
# compare the areas of two geometric objects
defissamearea
(g1, g2):
return g1.getarea() == g2.getarea()
main()
動態繫結的機制如下： 假設物件o是類c1,c2,c3,…,cn(c1是c2的子類，c2是c3的子類，… ,cn-1 是 cn 的子類，即cn是通用的類，c1是最特定的類)的例項。在python中，cn是object類。如果物件o呼叫乙個方法p,那麼python會依次在類c1,c2,…,cn中查詢方法p的實現,直到找到為止。一旦找到乙個實現，就會停止查詢然後呼叫這個第一次找到的實現。
多型，動態繫結
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動態繫結和多型
動態繫結是指 在執行期間 即非編譯期 判斷所引用物件的實際型別，根據其實際的型別呼叫其相應的方法。多型的存在有三個必要條件 1，要求繼承 2，要有重寫 3，父類引用指向子類物件 例 class animal public void enjoy class cat extends animal pub...
多型 動態繫結 實驗
定義三個類，父類geometricobject代表幾何形狀，子類circle代表圓形，myrectangle代表矩形。定義乙個測試類test，編寫equalsarea方法測試兩個物件的面積是否相等 注意方法的引數型別，利用動態繫結技術 編寫displaygeometricobject方法顯示物件的面...