greenlet手动切换协程
from greenlet import greenlet

def tes_1():
    print(12)
    gr2.switch()#协程手动切换
    print(34)
    gr2.switch()#协程切换

def tes_2():
    print(56)
    gr1.switch()#协程切换
    print(78)

gr1 = greenlet(tes_1)  #生成两个协程
gr2 = greenlet(tes_2)
gr1.switch()#协程切换

gevent自动切换协程
 import gevent
 
 def foo():
     print("running in foo")
     gevent.sleep(2) #IO阻塞2秒 自动切换下一个协程
     print('Explict context switch to foo again')
 def bar():
     print("Explicit精确的 context上下文切换 to bar")
     gevent.sleep(1)#IO阻塞1秒
     print('Implicit context switch back to bar')
 def func3():
     print("running func3")
     gevent.sleep(0)#IO不阻塞，释放 就先执行下面代码
     print("running func3 again")
 
 gevent.joinall([
     gevent.spawn(foo),#生成协程
     gevent.spawn(bar),
     gevent.spawn(func3),
 ])