python面向对象之内置函数.__str__,__repr__,__del__

#__str__打印对象使不返回对象内存地址，返回指定内容
class Student:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex
    def __str__(self):
        return '{name:%s,age:%s,sex:%s}'%(self.name,self.age,self.sex)

s1 = Student('ryan',18,'male')
print(s1)
#{name:ryan,age:18,sex:male}

__repr__,作用同__str__，若两者都存在，则执行__str__：

class Student:
    def __init__(self,name,age):
        self.name = name
        self.age = age
    def __repr__(self):
        print('__repr__')
        return self.name
    def __str__(self):
        print('__str__')
        return self.name
s1 = Student('ryan',12)
print(s1)
#__str__
#ryan

 

__del__,删除操作系统调用的资源，如果不执行del操作，会在程序执行完，自动调用__del__，如果执行del操作，会立刻关闭掉被调用的资源

class OpenFile:
    def __init__(self,filename):
        self.filename = filename

    def __del__(self):
        print('删除操作系统相关资源...')

f1 = OpenFile('a.py')
print('is success?')

#is success?
#删除操作系统相关资源...