迭代器--》生成器--》协程的关系与区别

判断xxx_obj是否可以迭代

在第1步成立的前提下，调用 iter 函数得到 xxx_obj 对象的 __iter__ 方法的返回值

__iter__ 方法的返回值是一个迭代器

如果想要一个对象称为一个 可以迭代的对象，即可以使用for,必须实现 __iter__方法

__iter__ 中必须返回对象的引用【要这个对象有__iter__和__next__方法, 实际上取的__next__的返回值】

迭代器结束，需要抛出一个 StopIteration 异常。

def create_num(all_num):
    # a = 1
    # b = 1
    a, b = 0, 1
    current_num = 0
    while current_num < all_num:
        yield a              # 如果一个函数中有yield语句，那么这个就不在是函数，而是一个生成器的模板
        a, b = b, a + b
        current_num += 1
 
 
if __name__ == ‘__main__‘:
    # 如果在调用create_num的时候，发现这个函数有yield，此时不是调用函数，而是创建一个生成器对象
    obj = create_num(10)
    for num in obj:
        print(num)

def create_num(all_num):
    a, b = 0, 1
    current_num = 0
    while current_num < all_num:
        res = yield a
        print(">>>>ret>>>>", res)
        a, b = b, a + b
        current_num += 1
 
 
if __name__ == ‘__main__‘:
    obj = create_num(4)
    # obj.send(None) # send一般不会放到第一次启动生成器，如果非要如此，传递None
    ret = next(obj)
    print(ret)
    ret = obj.send("hhhhh")
    print(ret)
    # send里面的数据,会传递给第5行，当作yield a的结果,然后res保存这个结果..
    # send的结果是下一次调用yield时，yield后面的值
    ret = obj.send(None)
    print(ret)
    ret = obj.send(None)
    print(ret)

#!/bin/python3
# -*- coding=utf-8 -*-
 
import time
def task_1():
    while True:
        print("------1-------")
        time.sleep(0.1)
        yield 
 
 
def task_2():
    while True:
        print("------2------")
        time.sleep(0.2)
        yield 
 
 
def main():
   t1 = task_1()
   t2 = task_2()
   while True:
       next(t1)
       next(t2)
if __name__ == "__main__":
    main()

#!/bin/python3
# -*- encoding=utf-8 -*-
 
from greenlet import greenlet
import time
def test1():
    while True:
        print("----A----")
        gr2.switch()
        time.sleep(0.5)
def test2():
    while True:
        print("----B----")
        gr1.switch()
        time.sleep(0.5)
gr1 = greenlet(test1)
gr2 = greenlet(test2)
# 切换到gr1中执行
gr1.switch()

#!/bin/python3
# -*-encoding=utf-8-*-
 
import gevent
import time 
def f1(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        gevent.sleep(0.5)
def f2(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        gevent.sleep(0.5)
def f3(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        gevent.sleep(0.5)
print("----1-----")
g1 = gevent.spawn(f1, 5)
print("----2-----")
g2 = gevent.spawn(f2, 5)
print("----3-----")
g3 = gevent.spawn(f3, 5)
print("----4-----")
g1.join()
g2.join()
g3.join()

#!/bin/python3
# -*-encoding=utf-8-*-
 
import gevent
from gevent import monkey 
import time 
monkey.patch_all()
def f1(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        time.sleep(0.5)
#        gevent.sleep(0.5)
 
def f2(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        time.sleep(0.5)
 #       gevent.sleep(0.5)
 
def f3(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        time.sleep(0.5)
#        gevent.sleep(0.5)
 
print("----1-----")
g1 = gevent.spawn(f1, 5)
print("----2-----")
g2 = gevent.spawn(f2, 5)
print("----3-----")
g3 = gevent.spawn(f3, 5)
print("----4-----")
g1.join()
g2.join()
g3.join()

#!/bin/python3
# -*-encoding=utf-8-*-
 
import gevent
from gevent import monkey 
import time 
monkey.patch_all()
def f1(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        time.sleep(0.5)
#        gevent.sleep(0.5)
 
def f2(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        time.sleep(0.5)
 #       gevent.sleep(0.5)
 
def f3(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        time.sleep(0.5)
#        gevent.sleep(0.5)
 
gevent.joinall([
    gevent.spawn(f1, 5), 
    gevent.spawn(f2, 5), 
    gevent.spawn(f3, 5)
    ])  

#!/bin/python3
#-*- encoding=utf-8 -*-
 
import gevent 
import urllib.request 
from gevent import monkey
monkey.patch_all()
def downloader(img_name, img_url):
    req = urllib.request.urlopen(img_url)
    img_content = req.read()
      
    with open("./img/"+ img_name, "wb") as f:
        f.write(img_content)
def main():
    gevent.joinall([
            gevent.spawn(downloader, "1.jpg", ‘https://rpic.douyucdn.cn/asrpic/190417/5440020_3968619_65b10_2_2142.jpg‘),
            gevent.spawn(downloader, ‘2.png‘, "https://rpic.douyucdn.cn/asrpic/190417/594613_2143.png")
        ])  
if __name__=="__main__":
    main()