面向对象的进阶

首先先说两个模块，今天刚认识的两个内置函数：

isinstance：

判断一个变量是不是另一个变量的对象，对返回True，错Flase

class A:
    name='二狗'
    def __init__(self):
        pass
b=3
a=A()

print(isinstance(a,A))
print(isinstance(b,A))

 

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
True

Process finished with exit code 0

 

issubclass：

判断类的关系，子父类，，对返回True，错Flase

class A:
    name='二狗'
    def __init__(self):
        pass

class b(A):
    anme='打钩'
    def __init__(self):
        pass
print(issubclass(b,A))

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
True

Process finished with exit code 0

一，反射

其实说白了，反射就是用字符串类型的名字去操作变量

反射中主要要介绍的四种方法hasattr  getattr  setattr delattr

1，反射对象中的属性和方法：

class A:
    name='二狗'
    def func(self):
        print('你好')
a=A()
print(getattr(a,'name'))
print(getattr(A,'name'))

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
二狗
二狗

Process finished with exit code 0

class A:
    name='二狗'
    def func(self):
        print('你好')
a=A()
ret=getattr(a,'func')
ret()

你好

Process finished with exit code 0

用类名调方法

class A:
    name='二狗'
    @classmethod
    def func(self):
        print('你好')
a=A()
ret=getattr(a,'func')
ret()
ret=getattr(A,'func')
ret()

有的时候为了防止我们执行的变量函数里没有会报错，所以通常getattr会和hasattr合起来用

class A:
    name='二狗'
    @classmethod
    def func(self):
        print('你好')
if hasattr(A,'fun'):
    ret=getattr(A,'fun')
    ret()

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe

Process finished with exit code 0

有的时候用的用户交互，我们还可设置输入的什么，我们就可以直接调用：

class A:
    name='二狗'
    def func(self):
        print('你好')
a=A()
b=input('>>>>>>')
print(getattr(a,b))
print(A.__dict__[b])

反射模块的属性

import mm
print(mm.day)
print(getattr(mm,'day'))

Monday
Monday

Process finished with exit code 0

反射内置模块

import time
print(getattr(time,'time')())
print(getattr(time,'asctime')())

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
1516607396.7829843
Mon Jan 22 15:49:56 2018

Process finished with exit code 0

反射自己模块中的变量

import sys
def func():
    print('你好')
name='二狗'

print(sys.modules['__main__'].name)
print(getattr(sys.modules['__main__'],'name'))

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
二狗
二狗

Process finished with exit code 0

调用自己模块中函数

import sys
def func():
    print('你好')
name='二狗'
print(getattr(sys.modules['__main__'],'func')())

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
你好
None

Process finished with exit code 0

__main__是写死的，有的时候我们可以是它灵活一点，把它换成__name__就好了

import sys,mm
def func():
    print('你好')
name='二狗'
getattr(sys.modules['__main__'],'func')()
na=input('....')
print(getattr(sys.modules[__name__],na))

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
你好
....name
二狗

Process finished with exit code 0

如果函数有参数反射的话直接在后面加上就好了

import time
print(time.strftime('%Y-%m-%d %H:%M:S'))
print(getattr(time,'strftime')('%Y-%m-%d %H:%M:S')
)

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
2018-01-22 16:16:S
2018-01-22 16:16:S

Process finished with exit code 0

反射一个模块中的类

import mm
mm.C
print(getattr(mm,'C'))

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
erha
<class 'mm.C'>

Process finished with exit code 0

 

setattr   设置修改变量

class A:
    name='二狗女'
    def func(self):
        print('不好')
a=A()
setattr(a,'name','大狗')
print(a.name)
print(A.name)
print(getattr(a,'name'))
print(getattr(A,'name'))
setattr(A,'name','alex')
print(A.name)

大狗
二狗女
大狗
二狗女
alex

delattr删除变量

class A:
    name='二狗女'
    def func(self):
        print('不好')
a=A()
setattr(a,'name','大狗')
print(a.name)
delattr(a,'name')
print(a.name)
delattr(A,'name')
print(a.name)

大狗
Traceback (most recent call last):
二狗女
  File "C:/s9/day27/fanshe", line 60, in <module>
    print(a.name)
AttributeError: 'A' object has no attribute 'name'

Process finished with exit code 1

二，，类的内置方法

 

__str__

__repr__

 

class Teacher:
    def __init__(self,name,salary):
        self.name = name
        self.salary = salary
    def __str__(self):
        return "Teacher's object :%s"%self.name
    def __repr__(self):
        return str(self.__dict__)
    def func(self):
        return 'wahaha'
nezha = Teacher('哪吒',250)
print(nezha)  # 打印一个对象的时候，就是调用a.__str__
print(repr(nezha))
print('>>> %r'%nezha)

eacher's object :哪吒
{'name': '哪吒', 'salary': 250}
>>> {'name': '哪吒', 'salary': 250}

Process finished with exit code 0

# %s str()  直接打印 实际上都是走的__str__
# %r repr()  实际上都是走的__repr__
# repr 是str的备胎，但str不能做repr的备胎

# print(obj)/'%s'%obj/str(obj)的时候，实际上是内部调用了obj.__str__方法，如果str方法有，那么他返回的必定是一个字符串
# 如果没有__str__方法，会先找找父类中的__str__，再没有再本类中的__repr__方法

。 # repr(),只会找__repr__,如果没有找父类的

__len__

class Classes:
    def __init__(self,name):
        self.name = name
        self.student = []
    def __len__(self):
        return len(self.student)
    def __str__(self):
        return 'classes'
py_s9= Classes('python全栈9期')
py_s9.student.append('二哥')
py_s9.student.append('泰哥')
print(len(py_s9))
print(py_s9)

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/Users/hc/AppData/Local/Temp/Rar$DIa4724.16488/3.类的内置方法.py
2
classes

Process finished with exit code 0

__del__

析构方法，当对象在内存中被释放时，自动触发执行。

class Foo:

    def __del__(self):
        print('执行我啦')

f1=Foo()
del f1

:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
执行我啦

Process finished with exit code 0

__call__

对象后面加括号，触发执行。

class A:
    def __init__(self,name):
        self.name = name
    def __call__(self):
        for k in self.__dict__:
            print(k,self.__dict__[k])
a = A('alex')()

C:\Users\hc\AppData\Local\Programs\Python\Python36\python3.exe C:/s9/day27/fanshe
name alex

Process fini