I'm on Python 3.4 making a practice app to learn Python's asyncio module.
I've got several modules in my application:
app.py
import asyncio
import logging
class Client(asyncio.Protocol):
def __init__(self, loop):
self.loop = loop
def connection_made(self, transport):
print('Connection with server established')
self.transport = transport
def data_received(self, data):
data = data.decode()
print('Received: ', data)
if not int(data):
print('Stopping loop')
self.loop.stop()
else:
message = 'remove one'.encode()
self.transport.write(message)
print('Sent:', message)
def connection_lost(self, exc):
print('Connection with server lost.')
self.loop.stop()
loop = asyncio.get_event_loop()
fn = loop.create_connection(
lambda: Client(loop), '127.0.0.1', 9999
)
logging.basicConfig(level=logging.DEBUG)
client = loop.run_until_complete(fn)
try:
loop.run_forever()
except KeyboardInterrupt:
pass
print('Loop ended')
loop.close()
counter.py
import asyncio
class Counter:
def __init__(self, maxcount):
self.maxcount = maxcount
@asyncio.coroutine
def count(self):
yield from asyncio.sleep(self.maxcount)
print('Done counting')
serie.py
import asyncio
class Serie:
def __init__(self, loop, items=None):
self.loop = loop
self.items = items or []
@asyncio.coroutine
def remove_one(self, counter):
if len(self.items) is not 0:
yield from counter.count()
item = self.items.pop(0)
print('Removed', item)
else:
print('Serie is empty')
@asyncio.coroutine
def start_removing(self, counter):
while self.items:
yield from self.remove_one(counter)
print('Serie.start_removing() has finished')
mission_control.py
import asyncio
import logging
from counter import Counter
from serie import Serie
class MissionControl(asyncio.Protocol):
def __init__(self, loop, counter, serie):
self.loop = loop
self.counter = counter
self.serie = serie
def connection_made(self, transport):
print('Connection established with', transport.get_extra_info('peername'))
self.transport = transport
self.transport.write(str(len(self.serie.items)).encode())
def data_received(self, data):
data = data.decode()
print('Received:', data)
if data == 'remove one':
yield from self.serie.remove_one()
print('Removed one: {}'.format(self.serie.items))
self.transport.write(str(len(self.serie.items)).encode())
else:
print('Done')
def connection_lost(self, exc):
print('Connection with {} ended'.format(self.transport.get_extra_info('peername')))
logging.basicConfig(level=logging.DEBUG)
loop = asyncio.get_event_loop()
counter = Counter(2)
planets = Serie(loop, ['Mercúrio', 'Vênus', 'Terra', 'Marte',
'Júpiter', 'Saturno', 'Urano', 'Netuno'])
fn = loop.create_server(
lambda: MissionControl(loop, counter, planets), '127.0.0.1', 9999
)
server = loop.run_until_complete(fn)
print('Server started')
try:
loop.run_forever()
except KeyboardInterrupt:
pass
server.close()
loop.run_until_complete(server.wait_closed())
loop.stop()
loop.close()
You can also find the source at this Github gist.
In mission_control.py, the method data_received() appears not to be called when the client (app.py) sends data via its self.transport property.
Where is the implementation error and how can I fix it?
答案 0 :(得分：2)
The problem is that data_received is not (and cannot be) a coroutine, but you're using yield from inside it. Internally asyncio is just calling self.data_received(data) without any yield from call, which means the body of the method isn't being executed at all - instead a generator object is immediately returned. You need to refactor your implementation to not use yield from, which requires using callbacks instead:
class MissionControl(asyncio.Protocol):
def __init__(self, loop, counter, serie):
self.loop = loop
self.counter = counter
self.serie = serie
def connection_made(self, transport):
print('Connection established with', transport.get_extra_info('peername'))
self.transport = transport
self.transport.write(str(len(self.serie.items)).encode())
def data_received(self, data):
data = data.decode()
print('Received:', data)
if data == 'remove one':
fut = asyncio.async(self.serie.remove_one(self.counter))
fut.add_done_callback(self.on_removed_one)
else:
print('Done')
def on_removed_one(self, result):
print('Removed one: {}'.format(self.serie.items))
self.transport.write(str(len(self.serie.items)).encode())
def connection_lost(self, exc):
print('Connection with {} ended'.format(self.transport.get_extra_info('peername')))
Another option would be to use the asyncio Streams API instead of asyncio.Protocol, which will allow you to use coroutines:
import asyncio
import logging
from counter import Counter
from serie import Serie
@asyncio.coroutine
def mission_control(reader, writer):
counter = Counter(2)
serie = Serie(loop, ['Mercúrio', 'Vênus', 'Terra', 'Marte',
'Júpiter', 'Saturno', 'Urano', 'Netuno'])
writer.write(str(len(serie.items)).encode())
while True:
data = (yield from reader.read(100)).decode()
print('Received:', data)
if data == 'remove one':
result = yield from serie.remove_one(counter)
else:
print('Done')
return
print('Removed one: {}'.format(serie.items))
writer.write(str(len(serie.items)).encode())
logging.basicConfig(level=logging.DEBUG)
loop = asyncio.get_event_loop()
coro = asyncio.start_server(mission_control, '127.0.0.1', 9999, loop=loop)
server = loop.run_until_complete(coro)
# The rest is the same