python面向对象--类的内置函数

#isinstance(obj,cls)判断obj是否是类cls的实例
#issubclass(cls,cls1)判断cls是否是cls1的子类或派生类
class Foo:
    pass


class Bar(Foo):
    pass


print(issubclass(Bar,Foo))#检查sub类是否是super类的派生类

f1=Foo()
print(isinstance(f1,Foo))#检查是否obj是否是类cls对象

 

#自定义格式化的format方法
x='{0}{0}{0}'.format("dog")

print(x)


format_dic={
    'ymd':"{0.year}{0.mon}{0.day}",
    "m-d-y":"{0.mon}-{0.day}-{0.year}",
    "y:m:d":"{0.year}:{0.mon}:{0.day}"
}

class Date:
    def __init__(self,year,mon,day):
        self.year=year
        self.mon=mon
        self.day=day

    def __format__(self, format_spec):#改写系统内置的format属性
        print("我执行了")
        print("-->",format_spec)
        if format_spec:
            fm=format_dic[format_spec]
            return fm.format(d1)
        else:
            return "为空"

d1=Date(2016,12,26)
#format(d1)#d1.__format__()

print(format(d1))#d1.__format__()

print(format(d1,"ymd"))

d1.name="alex"
print(d1.name)
# x='{0.year}{0.mon}{0.day}'.format(d1)
# print(x)

 

###改变字符串的显示方法 str,repr

# l=list("hello")
#
# print(l)

# class Foo:
#     def __str__(self):
#         return "自己定制的对象的显示方式"
#
# f1=Foo()
# print(f1)#-->str(f1)-->f1.__str__()




# file=open("test.txt","w")
# print(file)


#自己定制str方法
class Foo:
    def __init__(self,name,age):
        self.name=name
        self.age=age

    # def __str__(self):#当前str与repr共存
    #     return "这是str"
    #
    # def __repr__(self):#repr或者交互式解释器
    #     return "名字是%s 年龄是%s" %(self.name,self.age)

f1=Foo("egon",19)

#repr(f1)-->f1.__repr__()

# print(f1)#str(f1)--->f1.__str__()----->f1.__repr__()

f1.__str__()
print(str(f1))

 

#call方法,对象通过()访问
class Foo:
    def __call__(self, *args, **kwargs):
        print("实例执行了obj")

f1=Foo()

f1()#foo下的.__call__

Foo()#abc下的__call__

 

#通过类的next和iter实现迭代器协议
class Foo:

    def __init__(self,n):
        self.n=n

    def __iter__(self):
        return self

    def __next__(self):
         if self.n==100:
             raise StopIteration("终止了")
         self.n+=1
         return self.n

# l=list('hello')
# for i in l:
#     print(i)

f1=Foo(10)
print(next(f1))
print(next(f1))
print(f1.__next__())


for i in f1: #f1.__iter__() ==iter(f1)
    print(i)#next(f1) for循环捕捉异常终止


class Fib:

    def __init__(self):
        self.a=1
        self.b=1

    def __iter__(self):
        return self

    def __next__(self):
        self.a,self.b=self.b, self.a+self.b
        if self.b>100:
            raise StopIteration("终止了")
        return self.a



f1=Fib()
print(next(f1))
print(next(f1))
print(next(f1))
print(next(f1))
print(next(f1))
print(next(f1))
print(next(f1))
print(next(f1))
print("=====>")
for i in f1:
    print(i)

 

class Foo:
    # __slots__ = ["name","age"]#{"name":none,"age":"none"}
    __slots__ = "name"#限定实例的数据属性,节省内存

f1=Foo()
f1.name="egon"
print(f1.name)

#f1.age=18 #__setattr__---->f1.__dict__["age"]=18

# print(f1.__dict__)

print(f1.__slots__)
print(f1.__slots__)