coroutine比较，lua的实现更科学一点。

co1.lua

function test1(co2)
    print(12)
    coroutine.resume(co2)
    print(34)
    coroutine.resume(co2)
end

function test2()
    print(56)
    coroutine.yield()
    print(78)
end

local co1 = coroutine.create(test1)
local co2 = coroutine.create(test2)
coroutine.resume(co1, co2)

co1.py

from greenlet import greenlet

def test1():
    print 12
    gr2.switch()
    print 34
    gr2.switch()

def test2():
    print 56
    gr1.switch()
    print 78

gr1 = greenlet(test1)
gr2 = greenlet(test2)
gr1.switch()