coroutine and yield

Inside a function, the yield statement can also be used as an expression that appears on the right side of an assignment operator.

A function that uses yield in this manner is known as a coroutine, and it executes in response to values being sent to it.

For example:

def receiver():

    print("Ready to receive")

    while True:

        n = (yield)

        print("Got %s" % n)

>>> r = receiver()

>>> r.next() # Advance to first yield (r._ _next_ _() in Python 3)

Ready to receive

>>> r.send(1)

Got 1

>>> r.send(2)

Got 2

>>> r.send("Hello")

Got Hello

>>>

In this example, the initial call to next() is necessary so that the coroutine executes statements leading to the first yield expression.

A coroutine will typically run indefinitely unless it is explicitly shut down or it exits on its own.To close the stream of input values, use the close() method like this:

>>> r.close()

>>> r.send(4)

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

StopIteration