list=[1,2,3,4]

it = iter(list)    # 创建迭代器对象

for x in it:

    print (x, end=" ")

import sys         # 引入 sys 模块

list=[1,2,3,4]

it = iter(list)    # 创建迭代器对象

while True:

    try:

        print (next(it))

    except StopIteration:

        sys.exit()

class MyNumbers:

  def __iter__(self):

    self.a = 1

    return self

  def __next__(self):

    x = self.a

    self.a += 1

    return x

myclass = MyNumbers()

myiter = iter(myclass)

print(next(myiter))

print(next(myiter))

print(next(myiter))

print(next(myiter))

print(next(myiter))

class MyNumbers:

  def __iter__(self):

    self.a = 1

    return self

  def __next__(self):

    if self.a <= 20:

      x = self.a

      self.a += 1

      return x

    else:

      raise StopIteration

myclass = MyNumbers()

myiter = iter(myclass)

for x in myiter:

  print(x)

import sys

def fibonacci(n): # 生成器函数 - 斐波那契

    a, b, counter = 0, 1, 0

    while True:

        if (counter > n):

            return

        yield a

        a, b = b, a + b

        counter += 1

f = fibonacci(10) # f 是一个迭代器，由生成器返回生成

while True:

    try:

        print (next(f), end=" ")

    except StopIteration:

        sys.exit()