Python学习记录之(五)-----类进阶篇

静态方法

类方法

属性方法

通过@staticmethod装饰器即可把其装饰的方法变为一个静态方法，什么是静态方法呢？其实不难理解，普通的方法，可以在实例化后直接调用，并且在方法里可以通过self.调用实例变量或类变量，但静态方法是不可以访问实例变量或类变量的，一个不能访问实例变量和类变量的方法，其实相当于跟类本身已经没什么关系了，它与类唯一的关联就是需要通过类名来调用这个方法

类方法通过@classmethod装饰器实现，类方法和普通方法的区别是， 类方法只能访问类变量，不能访问实例变量

属性方法的作用就是通过@property把一个方法变成一个静态属性

#-*- encoding:utf8 -*-
#Wind clear raise
 
class Dog():
 
    member = 0
 
    def __init__(self, name):
        self.name = name
    def walk(self):
        print("walk function")
 
    @staticmethod # 无法通过self访问属性、方法
    def talk(self):
        #self.walk()
        print("Talk now is: ", self.name)
 
class Animal(object):
    name = "类变量"
    def __init__(self, name):
        self.name = name
 
    @classmethod  # 设置方法只能访问类变量，无法访问类属性
    def talk(self):
        print("The Animal talk:", self.name)
 
class Person(object):
    def __init__(self, name):
        self.name = name
    @property   # 将一个方法设置为属性
    def eat(self): # 无法通过Person.eat()调用
        print(self.name, "is eating")
        return "hel"
 
d = Dog("DD")
#d.talk("aaaaa") #AttributeError: 'str' object has no attribute 'name'
d.talk(d)
 
a = Animal("Dark")
a.talk()
 
p = Person("Fengqingyang")
s = p.eat
print("return [%s]" % s)

Talk now is: DD
The Animal talk: 类变量
Fengqingyang is eating
return [hel]

二、特殊属性及成员

__doc__ __class__ __module__ __dict__

class Dog():
    """Dog doc content"""
###
#-*- encoding:utf8 -*-
#Wind clear raise
 
from 类的特殊属性方法_2  import Dog
 
class Foo(object):
    """doc内容"""
    def __init__(self, name):
        self.name = name
 
    def __call__(self, *args, **kwargs):
        print("__call__:", args, kwargs)
 
f = Foo("Wind")
print(Foo.__doc__)
print(f.__class__, f.__module__)
d = Dog()
print(d.__module__, d.__class__)
print(d.__doc__)
f("hello", name="test")
#Foo("")("call", age=333)
print(Foo.__dict__) # 类的所有属性成员
print(f.__dict__)  # 实例的所有属性成员
f.name = "dict测试"
print(Foo.__dict__)  # 结果内容不变
print(f.__dict__)  # 实例内容name变更
“”“
/Library/Frameworks/Python.framework/Versions/3.5/bin/python3.5 /data/youngboy/youngboy/study/day07/类的特殊属性方法.py
doc内容
<class '__main__.Foo'> __main__
类的特殊属性方法_2 <class '类的特殊属性方法_2.Dog'>
Dog doc content
__call__: ('hello',) {'name': 'test'}
{'__init__': <function Foo.__init__ at 0x1021df378>, '__module__': '__main__', '__call__': <function Foo.__call__ at 0x1021df400>, '__dict__': <attribute '__dict__' of 'Foo' objects>, '__doc__': 'doc内容', '__weakref__': <attribute '__weakref__' of 'Foo' objects>}
{'name': 'Wind'}
{'__init__': <function Foo.__init__ at 0x1021df378>, '__module__': '__main__', '__call__': <function Foo.__call__ at 0x1021df400>, '__dict__': <attribute '__dict__' of 'Foo' objects>, '__doc__': 'doc内容', '__weakref__': <attribute '__weakref__' of 'Foo' objects>}
{'name': 'dict测试'}
 
Process finished with exit code 0
 
”“”

2、__str__、__getitem__、__setitem__　　__delitem__

class Dog():
    """Dog doc content"""
    def __init__(self, name):
        self.name = name
 
    def __str__(self):  ##print(d)
        return "Wind"
    def test(self):
        pass
    def __getitem__(self, item): # 调用时触发
        print("getitem: ", item)
    def __setitem__(self, key, value):
        print("setitem: ", key, value) # 设置时触发
    def __delitem__(self, key): # 删除时触发
        print("del:", key)
 
d = Dog("Dog")
print(d)
 
result = d["k"]   # 触发 __getitem__
d["k"] = "setkey"  # 触发 __setitem
del d["k"]  # 触发__delitem__
"""

Wind
getitem: k
setitem: k setkey
del: k

"""

类的另类定义：

def func(self):
    print("hello Wind ", self.name, self.age)
 
def __init__(self,name, age):
    self.name = name
    self.age = age
 
# 利用逼格定义类， 同时也说明python一切皆对象
Foo = type('Foo2', (object,), {'talk': func, '__init__': __init__})
# 类名   type(object_or_name, bases, dict)
 
f = Foo("Wind", 33)
f.talk()
 
print(type(f))
print(type(Foo))

hello Wind Wind 33
<class '__main__.Foo2'>
<class 'type'>

类的生成 调用 顺序依次是 __new__ --> __call__ --> __init__

 class Foo(object):
     def __init__(self):
         print("init")
 
     def __call__(self, *args, **kwargs):
         print("hello call")
 
     def __new__(cls, *args, **kwargs):
         print("hello new")
         return  object.__new__(cls) # 去继承父类的__new__方法
         # 类似 F.__init__(self)
 
 f = Foo()

hello new
init

__new__  在实例化之前干点什么事

class Foo(object):
    def __init__(self, name):
        self.name = name
        print("init")
 
    def __call__(self, *args, **kwargs):
        print("hello call")
 
    def __new__(cls, *args, **kwargs):
        print("hello new")
        # return  object.__new__(cls) # 去继承父类的__new__方法
        # 类似 F.__init__(self)
 
f = Foo()
print(type(f))
 
程序结果 f 没有真正的创建，so,在init之前运行了new
<class 'NoneType'>

反射

class Foo(object):
    def walk(self):
        print("walk")
 
def talk(msg=""):
    print("hello talk")
 
s = input(">>").strip()
obj =Foo()
 
if hasattr(obj, s):
    v = getattr(obj, s)
    v()
 
else:
    setattr(obj, s, talk)
    v = getattr(obj, s)
    v()
 
print(dir(obj))
 
'''
>>input_str
hello talk
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'input_str', 'walk']
 
'''

异常：

 a = []
 s = {}
 s[1] = "hello"
 
 try:
     # a[3]
     # b
     # c = 1
     # s[2]
     open("aaa")
 except (IndexError, KeyError) as e:  # 多个异常写在一起
     print("异常 ", e)
 except NameError as e:  # 单个异常
     print("异常", e)
 except Exception as e:
     print("各种异常：", e)
 else: # 无异常
     print("无异常")
 finally: # 最终
     print("无论有无异常、表示感谢")
 
 class MyException(BaseException): # 自定义异常
     def __init__(self, msg):
         self.msg = msg
 
     # 重载父类 __str__， 父类默认直接 return self.msg
     # def __str__(self):
     #     print("str....") # 先输出 str...  然后输出msg
     #     return self.msg
 
 try:
     raise MyException("我的异常") # 直接抛出异常
 except MyException as e: #
     print("自定义： ", e)