Python中的迭代器和生成器详解

class Fib:
    def __init__(self, n):
        self.prev = 0
        self.cur = 1
        self.n = n
    def __iter__(self):
        return self
fib = Fib(5)
import collections
print('fib is Iterable? ', isinstance(fib, collections.Iterable))
print('fib is Iterator? ', isinstance(fib, collections.Iterator))
print(next(fib))

fib is Iterable?  True
fib is Iterator?  False
Traceback (most recent call last):
  File "D:/MyProject/Python/insight-tools-rest/test.py", line 27, in <module>
    print(next(fib))
TypeError: 'Fib' object is not an iterator

l = [1, 2, 3]
d = {'a': 1, 'b': 2, 'c': 3}
print(type(l))
print(type(d))
l = l.__iter__()
d = iter(d)
print(type(l))
print(type(d))

<class 'list'>
<class 'dict'>
<class 'list_iterator'>
<class 'dict_keyiterator'>

class Fib:
    def __init__(self, n):
        self.prev = 0
        self.cur = 1
        self.n = n
    def __iter__(self):
        return self
    def __next__(self):
        if self.n > 0:
            value = self.cur
            self.cur += self.prev
            self.prev = value
            self.n -= 1
            return value
        else:
            raise StopIteration()
fib = Fib(5)
import collections
print('fib is Iterable? ', isinstance(fib, collections.Iterable))
print('fib is Iterator? ', isinstance(fib, collections.Iterator))
print([i for i in fib])

def fib(n):
    prev = 0
    cur = 1
    while n > 0:
        yield cur
        n -= 1
        prev, cur = cur, cur + prev
        # tmp = prev
        # prev = cur
        # cur = cur + tmp
print([i for i in fib(5)])

fib = fib(5)
print(next(fib))
print(next(fib))
print(next(fib))
print(next(fib))
print(next(fib))