Python - 我怎樣才能更簡潔地使用生成器？

Question

（Python 3）

我正在使用Python生成器從隊列中讀取消息。

消費者讀取隊列消息後，它需要能夠告訴生成器在成功處理隊列消息時刪除隊列消息。爲了將.send（）發送到Python生成器，似乎我必須先將.send（None）發送給生成器。這使我的代碼比我認爲的應該更胖。

任何人都可以提出一種方式來使用qconsumer.py驅動發生器，使用更少的代碼行嗎？我已經確定了我希望消除的以下哪些行。

總之，如何讓下面的代碼更加緊湊，我如何刪除行的建議？下面

代碼爲qconsumer.py：下面

from qserver import Qserver 

myqserver = Qserver() 

myproducer = myqserver.producer() # trying to eliminate this line 
# first send to a generator must be None 
myproducer.send(None) # trying to eliminate this line 
for msg in myproducer: 
    # do something with message 
    print(msg) 
    if messageprocessok: 
     myproducer.send('delete') 

代碼爲qserver.py：

# -*- coding: utf-8 -*- 
import boto 
from boto.sqs.connection import SQSConnection 
from boto.sqs.message import Message 

QNAME = 'qinbound' 
SQSREGION = 'us-west-1' 

class Qserver(): 
    """A simple Q server.""" 

    def __init__(self, qname=None, sqsregion=None): 
     self.qname = qname or QNAME 
     self.sqsregion = sqsregion or SQSREGION 
     self.sqsconn = boto.sqs.connect_to_region(self.sqsregion) 
     self.q_in = self.sqsconn.get_queue(self.qname) 

    def producer(self): 
     while True: 
      qmessage = self.q_in.read(wait_time_seconds=20) 
      if qmessage is None: 
       continue 
      action = (yield qmessage.get_body()) 
      if action == 'delete': 
       # if processing completed ok, clear message from this queue 
       self.q_in.delete_message(qmessage) 

Answer 1

已經明白你想要做什麼，我想我會避免與混合send迭代。具有myqserver類是迭代器本身似乎更有意義，對我說：

# -*- coding: utf-8 -*- 
import boto 
from boto.sqs.connection import SQSConnection 
from boto.sqs.message import Message 

QNAME = 'qinbound' 
SQSREGION = 'us-west-1' 

class Qserver(): 
    """A simple Q server.""" 
    _current_message = None 

    def __init__(self, qname=None, sqsregion=None): 
     self.qname = qname or QNAME 
     self.sqsregion = sqsregion or SQSREGION 
     self.sqsconn = boto.sqs.connect_to_region(self.sqsregion) 
     self.q_in = self.sqsconn.get_queue(self.qname) 

    def __iter__(self): 
     return self 

    def __next__(self): 
     while True: 
      qmessage = self.q_in.read(wait_time_seconds=20) 
      if qmessage is not None: 
       self._current_message = qmessage 
       return qmessage 

    next = __next__ 

    def delete_current(self): 
     if self._current_message is not None: 
      self.q_in.delete_message(self._current_message) 

和使用將是這樣的：

from qserver import Qserver 

myqserver = Qserver() 
for msg in myqserver: 
    # do something with message 
    print(msg) 
    if messageprocessok: 
     myqserver.delete_current() 

Answer 2

您當前的消費者扔掉消息，因爲每個send調用返回一個。你應該這樣做，而不是：

myqserver = Qserver() 
myproducer = myqserver.producer() 
messageprocessok = False 
while True: 
    msg = myproducer.send('delete' if messageprocessok else None) 
    # do something with message 
    print(msg) 

或者：

myqserver = Qserver() 
myproducer = myqserver.producer() 
msg = next(myproducer) 
while True: 
    # do something with message 
    print(msg) 
    msg = myproducer.send('delete' if messageprocessok else None) 

，你需要單獨調用Qserver()和myqserver.producer()事實很簡單，因爲你做prouducer一個類的方法。或者，您可以使用獨立功能，或者創建一個簡單返回Qserver().producer()的包裝函數。這是獨立版本：

def producer(qname=None, sqsregion=None): 
    qname = qname or QNAME 
    sqsregion = sqsregion or SQSREGION 
    sqsconn = boto.sqs.connect_to_region(sqsregion) 
    q_in = sqsconn.get_queue(qname) 
    while True: 
     qmessage = q_in.read(wait_time_seconds=20) 
     if qmessage is None: 
      continue 
     action = (yield qmessage.get_body()) 
     if action == 'delete': 
      # if processing completed ok, clear message from this queue 
      q_in.delete_message(qmessage)