class Cat(): def bark(self): print("喵喵喵") def run(self): print("四条腿跑!") def sleep(self): print("趴着睡!") class Pig(): def bark(self): print("哼哼哼!") def run(self): print("四条腿跑!") def sleep(self): print("侧躺着睡!")# 一个用来管理动物的方法 只要你传入是一个动物 我就按照动物的标准来使用 完全不用考虑你具体是什么类型def management_animal(animal): print("==================正在溜%s=============" % animal.__class__.__name__) animal.bark() animal.run() animal.sleep()
判断一个对象是否是某个类的实例,结果为布尔类型
参数1 要判断的对象
参数2 要判断的类型
2.案例:
a = isinstance('own',str) # 判断对象是否字符串类型print(a) # True def add_num(a,b): if isinstance(a,int) and isinstance(b,int): # 判断是否是整型 return a+b return Noneprint(add_num(20,10)) # 30
参数一是子类
参数二是父类
2.案例:
class Animal: def eat(self): print("动物得吃东西...")class Pig(Animal): def eat(self): print("猪得吃 猪食....")a = issubclass(Pig,Animal)print(a) # Truep = Pig()b = issubclass(type(p),Animal)print(b) # True# 拓展print(type(p),p.__class__) #
class Person: def __init__(self,name,age): self.name = name self.age = age # 将对象转换为字符串时执行r def __str__(self): print("str run") return "my name is %s , age is %s" % (self.name,self.age)p = Person("rose",20)print(p) #在打印前都会现将要打印的内容转为字符串 通过调用__str__函数q = str(p)print(q)
# del使用案例class FileTool: """该类用于简化文件的读写操作 """ def __init__(self,path): self.file = open(path,"rt",encoding="utf-8") self.a = 100 def read(self): return self.file.read() # 在这里可以确定一个事,这个对象肯定不使用了 所以可以放心的关闭问文件了 def __del__(self): self.file.close()tool = FileTool("a.txt")print(tool.read())
#call 的执行时机class A: def __call__(self, *args, **kwargs): print("call run") print(args) print(kwargs)a = A()a(1,a=100) # call run (1,) {'a': 100}
# slots的使用import sysclass Person: __slots__ = ["name"] # 对象中只能添加'name'的属性,添加其他报错 def __init__(self,name): self.name = namep = Person("jck")# 查看内存占用print(sys.getsizeof(p)) # 48# p.age = 20 # 无法添加# dict 没有了print(p.__dict__) # 报错 因为类中有__slots__ 所以__dict__不存在了
class A: def __getattr__(self, item): print("__getattr__") return 1a = A()print(a.name) # __getattr__ 1
__getattribute__()
1.getattribute 该函数也是用来获取属性
在获取属性时先执行__getattribute__()。如果属性存在执行完__getattribute__()则不再执行
class A: def __getattr__(self, item): print("__getattr__") return 1 def __getattribute__(self, item): print("__getattribute__") # return self.__dict__[item] return super().__getattribute__(item)a = A()print(a.name) # __getattribute__ __getattr__ 1a.name = 'jack'print(a.name) # __getattribute__ jack
class A: def __setattr__(self, key, value): print(key) # name print(value) # jack print("__setattr__") self.__dict__[key] = valuea = A()a.name = "jack" # name jack __setattr__
class A: def __delattr__(self, item): print("__delattr__") print(item) self.__dict__.pop(item) passa = A()a.name = "jack"del a.name # __delattr__ name
[] 的实原理
getitem setitem delitem
class A: def __getitem__(self, item): print("__getitem__") return self.__dict__[item]a = A()a.name = "jack"print(a["name"]) # "jack"
class A: def __setitem__(self, key, value): print("__setitem__") self.__dict__[key] = valuea = A()a["name"] = "jack" # __setitem__
class A: def __delitem__(self, key): del self.__dict__[key] print("__delitem__")a = A()a.name = "jack"del a["name"] # __delitem__
class Student(object): def __init__(self,name,height,age): self.name = name self.height = height self.age = age def __gt__(self, other): # print(self) # print(other) # print("__gt__") return self.height > other.height def __lt__(self, other): return self.height < other.height def __eq__(self, other): if self.name == other.name and self.age == other.age and self.height == other.height: return True return Falsestu1 = Student("jack",180,28)stu2 = Student("jack",180,28)# print(stu1 > stu2) # 触发 __gt__(self, other)# print(stu1 < stu2) # 触发 __lt__(self, other)print(stu1 == stu2) # # 触发 __eq__(self, other)上述代码中,other指的是另一个参与比较的对象,大于和小于只要实现一个即可,符号如果不同 解释器会自动交换两个对象的位置 ,只能在同一个类中比较
# 实现一个自定义的rangeclass MyRange: def __init__(self,start,end,step): self.start = start self.end = end self.step = step def __iter__(self): return self def __next__(self): a = self.start self.start += self.step if a < self.end: return a else: raise StopIterationfor i in MyRange(1,10,2): print(i) # 1 3 5 7 9
当执行with 语句时,会先执行enter ,当代码执行完毕后执行exit,或者代码遇到了异常会立即执行exit,并传入错误信息包含错误的类型.错误的信息.错误的追踪信息 注意: enter 函数应该返回对象自己 exit函数 可以有返回值,是一个bool类型,用于表示异常是否被处理,仅在上下文中出现异常有用 如果为True 则意味着,异常以及被处理了 False,异常未被处理,程序将中断报错class MyOpen(object): def __init__(self,path): self.path = path def __enter__(self): self.file = open(self.path) print("enter.....") return self def __exit__(self, exc_type, exc_val, exc_tb): print("exit...") # print(exc_type,exc_val,exc_tb) self.file.close() return Truewith MyOpen("a.txt") as m: print(m) # enter..... <__main__.MyOpen object at 0x0000015CD88B84E0> exit...