[BangPypers] real use case of gevent context switch gevent.sleep(0)

[anu sree]

Thanks naufal and Krace.

I have tried following code. I have given gevent.sleep(0.1), that means
each greenlet let others to execute 0.1 secoond. But here each greenlet
waiting for others to complete, why?  Is it because of greenlet.joinall ?

Here I have created 3 greenlet threads (A, B, C). I think, A is the parent
greenlet, right ? Once C get finished control should goes to B, right ?
But here it going to A.
Please check the ouput.

import gevent

def task(num):
    thread_id = id(gevent.getcurrent())
    print "Start: ", num, thread_id

    for i in range(100000001):
        if i == 100000000:
            print num + str(i)

    gevent.sleep(0.1)

    for i in range(100000001):
        if i == 100000000:
            print num + str(i)

    print "End: ", num, thread_id

threads = [gevent.spawn(task, x) for x in ['A', 'B', 'C']]
gevent.joinall(threads)


Output
=======

Start:  A 139984038735696
A100000000
Start:  B 139984008421616
B100000000
Start:  C 139984008421776
C100000000
A100000000
End:  A 139984038735696
B100000000
End:  B 139984008421616
C100000000
End:  C 139984008421776