def func():
    print("====>1")
    yield 1
    print("====>2")
    yield 2
    print("====>3")
    yield 3

#生成器就是迭代器
g=func()
# g.__iter__()
# g.__next__()

res=next(g)
print(res)
#执行结果
====>1
1

#1、yield为我们提供了一种自定义迭代器的方法
#2、yield与return的区别：
    #1、yield可以放回多次值 
    #2、函数暂停与再继续的状态是由yield帮我们保存的

#代码
def my_range(start,end,step=1):
    while start < end:
        try:
            yield start
            start+=step
        except StopIteration:
            break

res=my_range(1,10)
for i in res:
    print(i)

import time
def tail(file_path):
    with open(file_path,"rb") as f:
        f.seek(0,2)
        while True:
            line=f.readline()
            if line:
                # print(line.decode("utf-8"),end="")
                yield line
            else:
                time.sleep(0.05)
def grep(lines,pattern):
    for line in lines:
        line=line.decode("utf-8")
        if pattern in line:
            print(line,end="")
lines=tail("file.txt")
grep(lines,"404")

def eater(name):
    print("{} ready eat".format(name))
    while True:
        food=yield
        print("{} start eat {}".format(name,food))

e=eater("alex")

#首先要初始化一下
next(e)      #第一次到yield暂停，这里也可以写成print(e.send(None))
#然后e.send()传值:1、从暂停的位置将值传给yiled,2、与next一样
e.send("apple")
e.send("鱼香肉丝")

//执行结果
alex ready eat
alex start eat apple
alex start eat 鱼香肉丝

def eater(name):
    print("{} ready eat".format(name))
    eat_list=[]
    while True:
        food=yield eat_list    #先将send传的值给yield，再由yield传给food，当暂停的时候将eat_list返回
        eat_list.append(food)
        print("{} start eat {}".format(name,food))

e=eater("alex")

#首先要初始化一下
next(e)      #第一次到yield暂停，这里也可以写成print(e.send(None))
#然后e.send()传值:1、从暂停的位置将值传给yiled,2、与next一样
print(e.send("apple"))
print(e.send("鱼香肉丝"))
//执行结果
alex ready eat
alex start eat apple
[‘apple‘]
alex start eat 鱼香肉丝
[‘apple‘, ‘鱼香肉丝‘]