Python类的继承(进阶5)
2024-08-25 00:18:13
转载请标明出处:
http://www.cnblogs.com/why168888/p/6411918.html本文出自:【Edwin博客园】
Python类的继承(进阶5)
1. python中什么是继承
python中什么是继承:
- 新类不必从头编写
- 新类从现有的类继承,就自动拥有了现有类的所有功能
- 新类只需要编写现有类缺少的新功能
继承的好处:
- 复用已有代码
- 自动拥有了现有类的所有功能
- 只需要编写缺少的新功能
继承的特点:
- 子类和父类是is关系
python继承的特点:
- 总是从某个类继承
- 不要忘记调用super().init
2. python中继承一个类
class Person(object):
def __init__(self, name, gender):
self.name = name
self.gender = gender
class Teacher(Person):
def __init__(self, name, gender, course):
super(Teacher, self).__init__(name, gender)
self.course = course
t = Teacher('Alice', 'Female', 'English')
print t.name
print t.course
3. python中判断类型
函数isinstance()可以判断一个变量的类型,既可以用在Python内置的数据类型如str、list、dict,也可以用在我们自定义的类,它们本质上都是数据类型。
class Person(object):
def __init__(self, name, gender):
self.name = name
self.gender = gender
class Student(Person):
def __init__(self, name, gender, score):
super(Student, self).__init__(name, gender)
self.score = score
class Teacher(Person):
def __init__(self, name, gender, course):
super(Teacher, self).__init__(name, gender)
self.course = course
t = Teacher('Alice', 'Female', 'English')
print isinstance(t, Person)
print isinstance(t, Student)
print isinstance(t, Teacher)
print isinstance(t, object)
4. python中多态
class Person(object):
def __init__(self, name, gender):
self.name = name
self.gender = gender
def whoAmI(self):
return 'I am a Person, my name is %s' % self.name
class Student(Person):
def __init__(self, name, gender, score):
super(Student, self).__init__(name, gender)
self.score = score
def whoAmI(self):
return 'I am a Student, my name is %s' % self.name
class Teacher(Person):
def __init__(self, name, gender, course):
super(Teacher, self).__init__(name, gender)
self.course = course
def whoAmI(self):
return 'I am a Teacher, my name is %s' % self.name
import json
class Students(object):
def read(self):
return r'["Tim", "Bob", "Alice"]'
s = Students()
print json.load(s)
5. python中多重继承
除了从一个父类继承外,Python允许从多个父类继承,称为多重继承。Java不能多继承
class A(object):
def __init__(self, a):
print 'init A...'
self.a = a
class B(A):
def __init__(self, a):
super(B, self).__init__(a)
print 'init B...'
class C(A):
def __init__(self, a):
super(C, self).__init__(a)
print 'init C...'
class D(B, C):
def __init__(self, a):
super(D, self).__init__(a)
print 'init D...'
class Person(object):
pass
class Student(Person):
pass
class Teacher(Person):
pass
class SkillMixin(object):
pass
class BasketballMixin(SkillMixin):
def skill(self):
return 'basketball'
class FootballMixin(SkillMixin):
def skill(self):
return 'football'
class BStudent(BasketballMixin):
pass
class FTeacher(FootballMixin):
pass
s = BStudent()
print s.skill()
t = FTeacher()
print t.skill()
6. python中获取对象信息
除了用 isinstance() 判断它是否是某种类型的实例外,还有没有别的方法获取到更多的信息呢?
首先可以用 type() 函数获取变量的类型,它返回一个 Type 对象
dir() 函数获取变量的所有属性
dir()返回的属性是字符串列表,如果已知一个属性名称,要获取或者设置对象的属性,就需要用 getattr() 和 setattr( )函数了
class Person(object):
def __init__(self, name, gender):
self.name = name
self.gender = gender
class Student(Person):
def __init__(self, name, gender, score):
super(Student, self).__init__(name, gender)
self.score = score
def whoAmI(self):
return 'I am a Student, my name is %s' % self.name
print type(123) # <type 'int'>
s = Student('Bob', 'Male', 88)
print s # <class '__main__.Student'>
print dir(123) # ['__abs__', '__add__', '__and__', '__class__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__', '__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__', '__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real']
print dir(s) # ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'gender', 'name', 'score', 'whoAmI']
print getattr(s, 'name') # Bob
setattr(s, 'name', 'Adam')
print s.name # Adam
class Person(object):
def __init__(self, name, gender, **kw):
self.name = name
self.gender = gender
for k, v in kw.iteritems():
setattr(self, k, v)
p = Person('Bob', 'Male', age=18, course='Python')
print p.age # 18
print p.course #Python
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