生成器

# 生成器
# def generator():
#     print(1)
#     return ‘a‘
#
# ret = generator()
# print(ret)

# 只要含有yield的函数就是生成器函数
# # 不能和return共存，需写在函数内部
# def generator():        # 函数的执行受外部控制
#     print(1)
#     yield ‘a‘
#     print(2)
#     yield ‘b‘
#     print(3)
#     yield ‘c‘
# # 生成器函数：执行之后会得到一个生成器作为返回值
# ret = generator()
# for i in ret:
#     print(i)
# # print(ret)
# # print(ret.__next__())
# # print(ret.__next__())
# # print(ret.__next__())

# 边生成数据边调用数据
# def wahaha():
#     for i in range(2000):
#         yield ‘哇哈哈%s‘ %i
# w = wahaha()
# count = 0
# for i in w:
#     count+=1
#     print(i)
#     if count>50:
#         break
#
# for i in w:
#     count+=1
#     print(i)
#     if count>100:
#         break
# def tell(file):
#     f= open(file,encoding=‘utf-8‘)
#     while True:
#         lin = f.readline()
#         if lin.strip():
#             yield lin.strip()   # 返回每一个值
# t = tell(‘feng‘)
# for i in t:
#     if ‘f‘ in i:            # 监听过滤
#         print(‘***‘ + i + ‘###‘)