decorator ＆ generator ＆ iterator

#!/usr/bin/python2.7
#coding:utf-8
#如果想有中文注释就必须得有上面的语句
__metaclass__ = type

#generator
def countDown(n):
    print("Start to count from " + str(n))
    while n > 0:
        yield n
        n -= 1
    print("Done!")

#iterator
#迭代器（iterator）：一个实现了__iter__()方法的对象是可迭代的，一个实现了next方法的对象是迭代器。
#for item in Fibs():  next()方法和__iter__()方法缺一不可;__iter__()仅调用一次, next()调用多次（有多少个元素就调用多少次）
class Fibs(object):
    def __init__(self):
        self.a = 1
        self.b = 1

    #如果没有next()， 有__iter__()提示如下错误
    #TypeError: iter() returned non-iterator of type ‘Fibs‘
    def next(self):
        print("in next()")
        self.a, self.b = self.b, self.a + self.b
        return self.a

    #如果没有__iter__()(不管有没有next())则提示如下错误
    #TypeError: ‘Fibs‘ object is not iterable
    def __iter__(self):
        print("in __iter__()")
        return self

def main():
    for item in countDown(10):
        print(item)

    print("")   #newline

    print(type(Fibs))       #<type ‘type‘>
    print(type(Fibs()))     #<class ‘__main__.Fibs‘>

    for fib in Fibs():
        if fib > 1000:
            print(fib)
            break

if __name__ == ‘__main__‘:
    main()
else:
    print("Being imported as a module.")