day13生成器

day13生成器

# 生成器 —— 迭代器
# 生成器函数 —— 本质上就是我们自己写得函数
# 生成器表达式
#普通函数
# def generator():
#     print(1)
#     return 'a'
# ret = generator()
# print(ret)
#生成器函数:只要含有yield关键字的函数都是生成器函数
#yield不能和return共用且需要写在函数内部
def generator1():
    print(1)
    yield 'a'
#生成器函数：执行之后会得到一个生成器作为返回值
ret1 = generator1()
print(ret1)

print(ret1.__iter__())
print(ret1.__next__())

def generator():
    print(1)
    yield 'a'
    print(2)
    yield 'b'
    yield 'c'
g = generator()
ret = g.__next__()
print(ret)
ret = g.__next__()
print(ret)
ret = g.__next__()
print(ret)
#或者使用for循环
for i in g:
    print(i)

#娃哈哈%i
def wahaha():
    for i in range(2000000):
        yield '娃哈哈%s'%i
g = wahaha()
g1 = wahaha()
print(g.__next__())
print(g1.__next__())

g = wahaha()
count = 0
for i in g:
    count +=1
    print(i)
    if count > 50:
        break
# print('*******',g.__next__())
for i in g:
    count +=1
    print(i)
    if count > 100:
        break

#监听文件例子
def tail(filename):
    f = open(filename,encoding='utf-8')
    while True:
        line = f.readline()
        if line.strip():
            yield line.strip()

g = tail('file')
for i in g:
    if 'python' in i:
        print('***',i)