本文教程操作环境：windows7系统、Python 3.9.1，DELL G3电脑。
yield from本质：
for item in iterable: yield item的缩写版
代码示例：
def g(x): yield from range(x , 0, -1) yield from range(x) print(list(g(5)))
利用yield from语句向生成器（协程）传送数据：
def writer():
while True:
w = (yield)
print('>>', w)
def writer_wrapper(coro1):
coro1.send(None)
while True:
try:
x = (yield)
coro1.send(x)
except StopIteration:
pass
def writer_wrapper(coro2):
yield from coro2
