异步

from greenlet mport greenlet

def fun1():
    print(1)
    gr2.switch()
    print(2)
    gr2.switch()

def fun2():
    print(3)
    gr1.switch()
    print(4)
    gr1.switch()

gr1 = greenlet(fun1)
gr2 = greenlet(fun2)

gr1.switch()
#输出1324