Exercise 44: Inheritance Vs. Composition

class Parent(object):
    def __init__(self, **kwargs):
        if kwargs.has_key(‘age‘):
            self.__age = kwargs[‘age‘]
        if kwargs.has_key(‘sex‘):
            self.sex = kwargs[‘sex‘]
    def implicit(self):
        print "PARENT implicit()"
    def get_age(self):
        print self.__age
class Child(Parent):
    pass

dad = Parent(sex = ‘male‘, age = 45)
son = Child()
dad.implicit()
son.implicit()

解析**kwargs: http://stackoverflow.com/questions/5624912/kwargs-parsing-best-practice

两个下划线__开头为私有变量或私有函数。

class Parent(object):
    def altered(self):
        print "PARENT altered()"
class Child(Parent):
    def altered(self):
        print "CHILD, BEFORE PARENT altered()"
        super(Child, self).altered()
        print "CHILD, AFTER PARENT altered()"
dad = Parent()
son = Child()
dad.altered()
son.altered()

上面是更改继承。

class Other(object):
    def override(self):
        print "OTHER override()"
def implicit(self):
    print "OTHER implicit()"
def altered(self):
    print "OTHER altered()"
class Child(object):
    def __init__(self):
self.other = Other()
def implicit(self):
    self.other.implicit()
def override(self):
    print "CHILD override()"
def altered(self):
    print "CHILD, BEFORE OTHER altered()"
    self.other.altered()
    print "CHILD, AFTER OTHER altered()"
son = Child()
son.implicit()
son.override()
son.altered()

合成composition