Fabio Manganiello <i...@fabiomanganiello.com> added the comment:
+1
I have similar applications (both using multithreading and multiprocessing)
which rely upon waiting for events to be both set and unset. Some example
common pattern:
```
from multithreading import Thread, Event, Queue
import time
q = Queue()
reading = Event()
def read_from_device(device):
# Wait for the caller to signal that it's ready to receive
reading.wait()
data = get_data(device)
while data:
data = get_data(device)
q.put(data)
# Once we're done receiving data, wait for the caller to
# signal that it has received everything
while reading.is_set():
time.sleep(1)
# Do some other operations once all threads are in sync
release_device(device)
processor = threading.Thread(target=read_from_device, args=(device,))
processor.start()
# Do something else
reading.set()
# Get data from the processor
data = q.get()
while data:
preprocess_data(data)
data = q.get()
# Do something before we're ready to clean up everything
process_data()
# Signal to the processor that we're done
reading.clear()
```
Events (and I'd say that this also applies to Conditions) are supposed to be
symmetric - one can either wait for an event to be set or cleared - but the
implementation provided by the current API is definitely asymmetric - `wait()`
can be used to wait for an event to be set, but if you want to wait for it to
be cleared then the only provided approach is through a poll on `is_set()`.
----------
nosy: +BlackLight
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue40871>
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