python 迭代器和生成器

# 迭代器
# 往前不往后
# 集合元素
list0 = [1, 2, 'a']
iter0 = iter(list0)
for x in iter0:
    print(x)
iter0 = iter(list0)
while(1):
    try:
        print(next(iter0))
    except:
        break

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)


# 生成器
# 返回 yield 的值
# 是一个迭代器的函数
def yieldtest(a):
    while True:
        yield a + 1
        a = a + 1
iter0 = yieldtest(0)
print(next(iter0))
print(next(iter0))
print(next(iter0))


def fibo(n):
    a, b, count = 0, 1, 0
    while True:
        if count > n:
            return
        yield a
        a, b = b, a + b
        count += 1
iter0 = fibo(10)
while(1):
    try:
        print(next(iter0), end=" ")
    except:
        break