__next__,__iter__实现迭代器,斐波那契数列

迭代器__next__,__iter__

基于__next__和__iter__方法实现的迭代器

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')   #到100就终止，for循环并且不会抛出异常
        self.n+=1
        return self.n
f1 = Foo(10)
print(f1.__next__())    #这样取值，就会抛异常
for i in f1:
    print(i)

斐波那契数列

class Fib:
    def __init__(self):
        self._a=0
        self._b=1

    def __iter__(self):
        return self

    def __next__(self):
        self._a,self._b=self._b,self._a + self._b
        return self._a

f1=Fib()

print(f1.__next__())
print(next(f1))
print(next(f1))

for i in f1:
    if i > 100:
        break
    print('%s ' %i,end='')