Question

This is my callback function and I set the rcv_buffer to be global

def rx_callback(ok, payload):
    global n_rcvd, n_right, rcv_buffer
    n_rcvd += 1
    (pktno,) = struct.unpack('!H', payload[0:2])
    if ok:
        n_right += 1
        rcv_buffer.append((pktno, payload))

And in the main() I continuously check the buffer to see whether the buffer is empty:

   while 1:
        while len(rcv_buffer) > 0:
            (pktno, payload) = rcv_buffer.pop(0)
            print 'pktno = ', pktno, 'payload = ', payload[2:]

But I didn’t do any synchronizations! Can I be sure that my operations on the list will not crash?Thanks!

Answer 1

In CPython, this is safe due to the interpreted nature of the execution, and due to the Global Interpeter Lock (which ensures that only a single bytecode from a single thread is executing at any given time).

Other Python implementations might be quite so forgiving though…