概述
面向过程：分析解决问题的步骤，用函数把步骤实现，按顺序调用
函数式：将某功能代码封装到函数中，使用时直接调用函数
面向对象：对函数进行分类和封装，以对象为中心的编程
class Cat: #class创建类 Cat类名称类开头习惯大写 类不需要返回值
def __init__(self,name,type,sex) : # 根据类创建对象时自动执行
self.name=name
self.type=type
self.sex=sex
def call(self):
print("一只叫%s的%s正在喵喵叫" %(self.name,self.type))
def lick(self) :
print("一只%s正在舔毛" %self.type)
cat1=Cat(‘花小猫‘,‘布偶猫‘,‘女‘) #创建一个实例
cat2=Cat(‘喵小胖‘,‘胖橘‘,‘女‘)
print(cat1.__dict__) #实例的所有属性字典
print(cat2.__dict__)
cat1.call()#调用属性
cat2.lick()
#类的增删改查
class School:
country=‘china‘
def __init__(self,name,address):
self.name=name
self.address=address
def Recruit_students(self) :
print(‘%s正在招生‘%self.name)
#查看
print(School.country)
p1=School(‘bd‘,‘bj‘)
print(p1.__dict__)
print(p1.country)
#修改
School.country=‘Japan‘
print(School.country)
def text(self):
print(‘text‘)
School.Recruit_students=text
p1.Recruit_students()
#增加
School.type=‘full_time‘ #数据
print(School.type)
print(p1.type)
def exam(self,place):
print(‘%s正在%s考试‘%(self.name,place))
School.exam=exam
print(School.__dict__)
p1.exam(‘classroom‘)
#删除
del School.type
print(School.__dict__)
#实例的增删改查
class School:
country=‘china‘
def __init__(self,name,address):
self.name=name
self.address=address
def Recruit_students(self) :
print(‘%s正在招生‘%self.name)
p1=School(‘bd‘,‘bj‘)
print(p1.__dict__)
#查看
print(p1.name)
print(p1.Recruit_students)
#增加
p1.type=‘public‘
print(p1.__dict__)
print(p1.type)
#修改
p1.name=‘qh‘
print(p1.__dict__)
print(p1.name)
#删除
del p1.type
print(p1.__dict__)
组合
class School:
def __init__(self,name,address):
self.name=name
self.address=address
class Course:
def __init__(self,name,price,period,school):
self.name=name
self.price=price
self.period=period
self.school=school
s1=School(‘bd‘,‘bj‘)
c1=Course(‘python‘,‘10000‘,‘6‘,s1)
print(c1.school.name)
面向对象的三大特性：继承、多态、封装
继承
python2：新式类（广度继承），经典类（深度优先）
python3：新式类（广度优先）
继承顺序：
1、子类先于父类
2、多个父类根据它们在列表中的顺序检查
3、对下一个类存在两个选择，选择第一个父类
class A:
a=‘ff‘
class B(A):
pass
class C(A):
pass
class D(C):
pass
class E(D,C):
pass
print(E.a)
class Ahsn:
money=10
def __init__(self,name):
self.name=name
def eat(self):
print(‘%s吃苹果‘ %self.name)
class Bs:
money=100
def __init__(self,name):
self.name=name
def drink(self):
print(‘%s喝果汁‘%self.name)
class Cgh(Ahsn): #单继承
pass
class Djs(Ahsn,Bs): #多继承 （选择第一个父类）
pass
#接口继承
import abc
class All(metaclass=abc.ABCMeta):
@abc.abstractmethod
def read(self):
pass
@abc.abstractmethod
def write(self):
pass
class Disk(All):
def read(self):
print(‘disk read‘)
def write(self):
print(‘disk write‘)
class Cdrom(All):
def read(self):
print(‘cdrom read‘)
def write(self):
print(‘cdrom write‘)
多态
不同的对象调用同一个方法
class Animal:
def __init__(self,name,height):
self.name=name
self.height=height
def call(self):
if self.height<15:
print(‘%s喵喵叫‘%self.name)
else:
print(‘%s汪汪叫‘ %self.name)
class Dog(Animal):
pass
class Cat(Animal):
pass
d=Dog(‘泰日天‘,15)
c=Cat(‘喵小胖‘,10)
d.call()
c.call()
封装
#普通封装
class A:
start=‘china‘
def __init__(self,name,age,hometown):
self.name=name
self.age=age
self.hometown=hometown
def introduce(self):
print(‘我叫%s今年%s岁来自%s‘ %(self.name,self.age,self.hometown))
#加一个_python规定只能内部访问，只是规定实际上外部可以访问到
class B:
_start=‘china‘
def __init__(self,name,age,hometown):
self.name=name
self.age=age
self.hometown=hometown
def introduce(self):
print(‘我叫%s今年%s岁来自%s‘ %(self.name,self.age,self.hometown))
#加两个_只能内部访问，外部无法访问，可调用接口访问
class C:
__start=‘china‘
def __init__(self,name,age,hometown):
self.name=name
self.age=age
self.hometown=hometown
def introduce(self):
print(‘我叫%s今年%s岁来自%s‘ %(self.name,self.age,self.hometown))
def use(self):
return C.__start
类内置方法 __getattr__,__setattr__,__delattr__
class Sg:
x=1
def __init__(self,y):
self.y=y
def __getattr__(self, item):
print(‘执行__getattr__‘)
s=Sg(‘10‘)
s.xh #属性不存在时执行__getattr__
class Sg:
x=1
def __init__(self,y):
self.y=y
def __setattr__(self, key, value):
print(‘执行__setattr__‘)
self.__dict__[key]=value
s=Sg(10)
s.z=3
print(s.__dict__)
class Sg:
x=1
def __init__(self,y):
self.y=y
def __delattr__(self, item):
self.__dict__.pop(item)
print(‘执行__delattr__‘)
s=Sg(10)
del s.y
print(s.y)
反射
class Computer:
type=‘notebook‘
def __init__(self,name,place):
self.name=name
self.place=place
def play(self):
print(‘%s玩游戏很好用‘%self.name)
c=Computer(‘apple‘,‘Amercia‘)
print(hasattr(c,‘name‘)) #c是否可以调用name可以返回True,不可以返回False
print(hasattr(c,‘play‘))
func=getattr(c,‘play‘)
func()
print(getattr(c,‘name‘,‘没有这个属性‘)) #检查c中name对应的值
print(getattr(c,‘play‘,‘没有这个属性‘))
func=getattr(c,‘play‘)
func()
setattr(c,‘name‘,‘xiaomi‘) #修改
setattr(c,‘size‘,‘20‘) #增加
setattr(c,‘fg‘,lambda self:self.name+‘h‘)
print(c.fg(c))
print(c.__dict__)
delattr(c,‘name‘) #删除
print(c.__dict__)
动态导入模块
import importlib d=importlib.import_module(‘m.n‘) d.a()
添加字符串
class List(list):
def append(self, object):
if type(object) is str:
# list.append(self,object)
super().append(object)
else:
print(‘只能添加字符串‘)
l=List(‘helloworld‘)
l.append(‘fg‘)
print(l)
授权
import time
class Open:
def __init__(self,filename,mode=‘r‘,encoding=‘utf-8‘):
self.file=open(filename,mode,encoding=encoding)
self.mode=mode
self.encoding=encoding
def write(self,line):
t=time.strftime(‘%Y-%m-%d %X‘)
self.file.write(‘%s%s‘%(t,line))
def __getattr__(self, item):
return getattr(self.file,item)
o=Open(‘a.txt‘,‘r+‘)
o.write(‘11111\n‘)
o.write(‘内存不足\n‘)
o.seek(0)
print(o.write)
print(o.read())
__str__,__repr__
class F():
def __init__(self,name):
self.name=name
def __str__(self): #print 返回值必须是字符串
return ‘g‘
def __repr__(self): #解释器中显示 返回值必须是字符串
return ‘s‘
__format__ #自定制格式化方式
class Date:
def __init__(self,year,month,day):
self.year=year
self.month=month
self.day=day
def __format__(self, format_spec):
dic = {‘ymd‘: ‘{0.year}{0.month}{0.day}‘,
‘y:m:d‘: ‘{0.year}:{0.month}:{0.day}‘,
‘y-m-d‘: ‘{0.year}-{0.month}-{0.day}‘}
print(‘-->‘,format_spec)
if format_spec not in dic:
format_spec=‘ymd‘
x=dic[format_spec]
return x.format(self)
d=Date(‘2018‘,‘9‘,‘18‘)
print(format(d,‘ymd‘）
__iter__,__next__ #实现迭代器
class F:
def __init__(self,n):
self.n=n
def __iter__(self):
return self
def __next__(self):
if self.n==20:
raise StopIteration(‘stop‘)
self.n+=self.n
return self.n
f=F(1)
print(next(f))
print(f.__next__())
for i in f:
print(i)
isintance,issubclass
class A:
pass
class B(A):
pass
c=A()
print(isinstance(c,A)) #实例c是否属于A
print(issubclass(B,A)) #B是否是A的子类
__getattribute__ #调用的属性是否存在都会调用__getattribute__
class C:
def __init__(self,x):
self.x=x
def __getattr__(self, item):
print(‘getattr‘)
def __getattribute__(self, item):
print(‘getattribute‘)
raise AttributeError(‘抛出异常‘)
__getitem__,__setitem__,__delitem__ #以字典方式增删改查
class D:
def __init__(self,x):
self.x=x
def __getitem__(self, item):
print(‘getitem‘)
return self.__dict__[item]
def __setitem__(self, key, value):
self.__dict__[key]=value
print(‘setitem‘)
def __delitem__(self, key):
print(‘delitem‘)
self.__dict__.pop(key)
d=D(‘h‘)
print(d[‘x‘])
d[‘name‘]=‘ghy‘
del d[‘name‘]
print(d.__dict__)
slots属性 #实例无法调用__dict__,节省内存
class D:
__slots__ = ‘name‘
__doc__ #文档注释
class D:
‘中国‘
__slots__ = ‘name‘
d=D()
print(d.__doc__)
中国
__module__,__class__ #所在模块，所在类
class D:
__slots__ = ‘name‘
d=D()
print(d.__module__)
print(d.__class__)
__del__ #析构方法当对象在内存被释放时，立即触发__del__
class A:
def __init__(self,name):
self.name=name
def __del__(self):
print(‘-->‘)
a=A(‘ghy‘)
del a
print(‘==>‘)
-->
==>
__call__ #对象后面加（）触发执行
class A:
pass
def __call__(self, *args, **kwargs):
print(‘df‘)
a=A()
a()
斐波那契数列
class Q:
def __init__(self):
self.a=0
self.b=1
def __iter__(self):
return self
def __next__(self):
if self.a>100:
raise StopIteration(‘stop‘)
self.a,self.b=self.b,self.a+self.b
return self.a
q=Q()
print(next(q))
print(next(q))
print(next(q))
print(‘--->‘)
for i in q:
print(i)
数据描述符
class F:
def __get__(self, instance, owner):
print(‘get‘)
def __delete__(self, instance):
print(‘delete‘)
def __set__(self, instance, value):
print(‘set‘)
非数据描述符
class F:
def __get__(self, instance, owner):
print(‘get‘)
def __delete__(self, instance):
print(‘delete‘)
调用顺序：
类属性>数据描述符
class F:
def __get__(self, instance, owner):
print(‘get‘,‘-->‘)
def __delete__(self, instance):
print(‘delete‘)
def __set__(self, instance, value):
print(‘set‘)
class A:
x=F()
def __init__(self,n):
self.x=n
A.x=1
print(A.__dict__)
数据描述符>实例属性
class F:
def __get__(self, instance, owner):
print(‘get‘)
def __delete__(self, instance):
print(‘delete‘)
def __set__(self, instance, value):
print(‘set‘)
class A:
x=F()
def __init__(self,n):
self.x=n
a=A(‘g‘)
a.x=1
set
set
实例属性>非数据描述符
class F:
def __get__(self, instance, owner):
print(‘get‘)
class A:
x=F()
a=A()
a.x=1
print(a.__dict__)
{‘x‘: 1}
上下文管理协议
class Open:
def __init__(self,name):
self.name=name
def __enter__(self):
print(‘执行enter‘)
return self
def __exit__(self, exc_type, exc_val, exc_tb): #exc_type异常类，exc_val异常值，exc_tb追踪信息若无异常均为None
print(‘执行exit‘)
print(exc_tb)
with Open(‘a.txt‘) as f: #触发__enter__ 得到的返回值交给f
print(f)
# print(g) #如果有异常从异常处触发运行__exit__ 如果返回True 可继续运行下面代码 else直接显示异常
print(‘==‘)
描述符
class A:
def __init__(self,x,y):
self.x=x
self.y=y
def __get__(self, instance, owner):
print(‘get‘)
# print(‘instance参数%s‘ %instance)
# print(‘owner参数%s‘ %owner)
return instance.__dict__[self.x]
def __set__(self, instance, value):
print(‘set‘)
# print(‘instance参数%s‘ % instance)
# print(‘value参数%s‘ %value)
if not isinstance(value,self.y):
raise TypeError(‘%s传入数值不是%s‘ %(self.x,self.y))
instance.__dict__[self.x]=value
def __delete__(self, instance):
print(‘delete‘)
instance.__dict__.pop(self.x)
def a(**kwargs):
def b(obj):
print(‘==>‘)
for key,value in kwargs.items():
setattr(obj,key,A(key,value))
return obj
print(‘-->‘)
return b
@a(name=str,age=int)
class B:
# name=A(‘name‘,str)
# age=A(‘age‘,int)
def __init__(self,name,age):
self.name=name
self.age=age
b=B(‘ghy‘,18)
print(b.__dict__)
print(b.name)
del b.name
print(B.__dict__)
装饰器
def a(**kwargs):
def b(obj):
print(‘==>‘)
for key,value in kwargs.items():
setattr(obj,key,value)
return obj
print(‘-->‘)
return b
@a(x=1,y=1)
class C:
pass
print(C.__dict__)
自定制property
class Userproperty:
def __init__(self,fun):
self.fun=fun
def __get__(self, instance, owner):
print(‘get‘)
# print(instance)
# print(owner)
if instance is None:
return self
res=self.fun(instance)
setattr(instance,self.fun.__name__,res) #将第一个得到的字典放入__dict__中，再次执行直接调取
return res
# def __set__(self, instance, value):
# pass
class B:
def __init__(self,name,length,width):
self.name=name
self.length=length
self.width=width
@Userproperty
def area(self):
return self.length*self.width
b=B(‘home‘,20,20)
print(b.area)
print(b.__dict__)
print(b.area)
print(b.area)
class A:
def __init__(self):
self.original_price=100.0
self.discount=0.8
@property
def price(self):
user_price=self.original_price*self.discount
return user_price
@price.setter
def price(self,value):
self.original_price=value
@price.deleter
def price(self):
del self.original_price
a=A()
print(a.price)
a.price=200
print(a.price)
del a.price
元类 #产生类的类
class A:
pass
a=A()
print(type(a))
print(type(A))
def __init__(self,name):
self.name=name
def test(self) :
pass
B=type(‘B‘,(object,),{‘x‘:1,‘__init__‘:__init__,‘test‘:test})
print(B.__dict__)
建立类的两种方法
class Mytype(type):
def __init__(self,a,b,c):
print(‘元类的构造函数执行‘)
def __call__(self, *args, **kwargs):
obj=object.__new__(self)
self.__init__(obj,*args,**kwargs)
return obj
class A(metaclass=Mytype):
def __init__(self,name):
self.name=name
a=A(‘ghy‘)
print(a.__dict__)
自定义元类
原文地址：https://www.cnblogs.com/ghy594820543/p/9643594.html
时间： 2024-08-03 04:31:46