Understanding this generator function

[Hussein B]

Hey,
This is an example of a generator function:
=====
def counter(start_at=0):
count = start_at
while True:
val = (yield count)
if val is not None:
count = val
else:
count += 1
======9
======
I'm not able to understand how this generator function is working,
would you please me (what happens when calling next/send)?
Thanks.

 

[James Mills]

Hi,

There is a great set of slides on this topic
available here: http://www.dabeaz.com/generators/

They explain this concept quite well and
walk you through everything you need to
know about generators and how powerful
they can be.

Please read it.

cheers
James

 

[Jeff]

def counter(start_at=0):

    count = start_at
    while True:
        val = (yield count)

A generator can accept a value from the consumer. So, If I have a
counter:

c = counter()

I can send it a value:

c.send(9)

        if val is not None:
            count = val

The generator tests to see it it received anything, and if it does,
resets count to what it received (in this case, 9).

        else:
            count += 1

Otherwise, it just increments count on each call.