yield与gen.coroutine

def d():

    for i in range(2):

        yield i

def b():

    yield d()

    print("b")

    yield "bb"

def a():

    g_b = b()

    print(g_b)

    g_d = next(g_b)

    print(g_d)

    v_d = next(g_d)

    print(v_d) #

    v_d = next(g_d)

    print(v_d) #

    b_next = next(g_b)

    print(b_next) # bb

if __name__ == "__main__":

    a()

#---输出

# <generator object b at 0x00000000033A3E60>

# <generator object d at 0x000000000389F150>

#

#

# b

# bb

----------------------

def d():

    for i in range(2):

        yield i

def b():

    yield d()

    print("b")

def a():

    g_b = b()

    print(g_b) # <generator object b at 0x00000000033A3E60>

    g_d = next(g_b)

    print(g_d) # <generator object d at 0x000000000389F150>

    v_d = next(g_d)

    print(v_d) #

    v_d = next(g_d)

    print(v_d) #

    b_next = next(g_b)

    print(b_next)

#---输出

<generator object b at 0x00000000033A3E60>

<generator object d at 0x000000000349F150>

0

1

b

Traceback (most recent call last):

  File "E:\eclipse-workspace\demo_python\demo\yield_demo.py", line 49, in <module>

    a()

  File "E:\eclipse-workspace\demo_python\demo\yield_demo.py", line 19, in a

    b_next = next(g_b)

StopIteration

----------------------

def d():

    for i in range(2):

        yield i

def b():

    yield d()

    print("b")

    yield

def a():

    g_b = b()

    print(g_b) # <generator object b at 0x00000000033A3E60>

    g_d = next(g_b)

    print(g_d) # <generator object d at 0x000000000389F150>

    v_d = next(g_d)

    print(v_d) #

    v_d = next(g_d)

    print(v_d) #

    b_next = next(g_b)

    print(b_next)

#---输出

<generator object b at 0x00000000033A3E60>

<generator object d at 0x000000000349F150>

0

1

b

None

--------------

@gen.coroutine

def gen_d():

    for i in range(10):

        raise gen.Return(i)

@gen.coroutine

def gen_b():

    v = yield gen_d()

    print("b")

@gen.coroutine

def gen_a():

    var = yield gen_b()

    print(var)

if __name__ == "__main__":

    ioloop.IOLoop.current().run_sync(gen_a)

--输出

b

None

-----------------------------

说明：方法gen_d的注解gen.coroutine去掉之后，

gen_d的返回值不再是Future类型，gen_b方法在执行以一条语句之后，

不会继续执行后面的语句

#@gen.coroutine

def gen_d():

    for i in range(10):

        raise gen.Return(i)

@gen.coroutine

def gen_b():

    v = yield gen_d()

    print("b")

@gen.coroutine

def gen_a():

    var = yield gen_b()

    print(var)

if __name__ == "__main__":

    ioloop.IOLoop.current().run_sync(gen_a)

--输出

0

 -----------------------------

yield直接返回

@gen.coroutine

def gen_d():

    for i in range(10):

        raise gen.Return(i)

@gen.coroutine

def gen_b():

    yield gen_d()

@gen.coroutine

def gen_a():

    var = yield gen_b()

    print(var)

if __name__ == "__main__":

    ioloop.IOLoop.current().run_sync(gen_a)

---

输出：None

----------------------

raise返回：

@gen.coroutine

def gen_d():

    for i in range(10):

        raise gen.Return(i)

@gen.coroutine

def gen_b():

    raise gen.Return(gen_d())

@gen.coroutine

def gen_a():

    var = yield gen_b()

    print(var)

if __name__ == "__main__":

    ioloop.IOLoop.current().run_sync(gen_a)

输出：<Future finished result=0>

--------------------------------

有异步的情况下不能直接返回：

@gen.coroutine

def gen_d():

    url = "http://x.x.x.x:8060/api/v1/health"

    result = yield AsyncHTTPClient(defaults=dict(request_timeout=10)).fetch(url, method="GET")

    raise gen.Return((result.code, result.body))

@gen.coroutine

def gen_b():

    raise gen.Return((yield gen_d()))

@gen.coroutine

def gen_a():

    var = yield gen_b()

    print(var)

if __name__ == "__main__":

    ioloop.IOLoop.current().run_sync(gen_a)

输出：(200, b'ok')