Python -- Records项目学习

Records学习笔记

Records链接地址

1. __getitem__(self, key) 内建方法(Build-in)

例子:

 class Test(object):

     def __getitem__(self, key):

         print("test")

         return 1

 t = Test()

 print(t["m"])

运行结果:

>>> hello
>>> 1

　　

2. ___getattr__(self, name) 内建方法(Build-in)

该方法在未找到对象的属性值的时候调用.

例子:

 class Test(object):
     def __getattr__(self, name):
         print("test")
         return 1

 t = Test()
 print(t.m)

运行结果:

>>> hello
>>> 1

去掉__getattr__函数时,会提示没有m这个属性的错误。

3. @property 装饰器

用于将一个函数生产对应的getter函数

实例:

class Test(object):
    @property
    def name(self):
        return self._name
    @name.setter
    def name(self, name):
        self._name = name

t = Test()
t.name = "hello"
print(t.name)

运行结果:

>>> hello

4. A if 条件 else B(语法)

print("") if __name__=='__main__' else print("")

5. __enter__和__exit__内建方法(Build-in)

用于with语句块,当进入with语句块的时候调用__enter__

当离开with语句块的时候调用__exit__

例子:

 class test(object):
     def __enter__(self):
         print("enter")
         return self
     def __exit__(self, type, value, traceback):
         print("out")
         del self
 with test() as m:
     m.name = 1
     print (m.name)

运行结果:

>>> enter
>>> 1
>>> out

6.  __iter__(self) 迭代器(Build-in)

通过__iter__函数获得一个迭代器对象, 调用迭代器的next方法不断获得下一个值.

例子:

 class test(object):
     def __init__(self):
         self.a = 1
         self.b = 1
     def __iter__(self):
         return self
     def __next__(self):
         test = self.a + self.b
         self.a, self.b = self.b, test
         return self.a
     def next(self):
         return self.__next__

 for i in test():
     if i > 1000:
         break
     print(i)