如何线程中通信？

需求：
我们通过intrinio.com获取了多支股票csv数据文件，并将其转换为xml文件
由于全局解释器锁的存在，多线程进行CPU 密集型操作并不能提高执行效率，我们修改程序构架：
1、使用多个DownloadThread线程进行下载(I/O操作)
2、使用一个ConvertThread线程进行转换(CPU密集型操作)
3、下载线程把下载数据安全地传递给转换线程

思路：
使用标准库中Queue.Queue，它是一个线程安全的队列，Download线程把下载的数据放入队列，Convert线程从队列中提取数据，它在内部实现了锁，帮助我们完成了同步工作

代码：

import csv
from xml.etree.ElemenTree import Element, ElementTree
import requests
from StringIO import StringIO
from xml_pretty import pretty
# 全局解释器锁(GIL)，python中的多线程处理CPU密集型任务时，需要获取GIL才可以进行任务处理，而且一个线程获取了GIL锁，另一个线程就不能获取，导致效率不高。同一时刻只有一个CPU来运行CPU密集型操作。GIL是属于进程的，如果是两个进程间的线程，那么这个锁是没有用的。每个进程有自己的GIL，进程间是相互独立的。
from Queue import Queue 

class DownloadThread(Thread):
    def __init__(self,sid,queue):
        Thread.__init__(self)
        self.sid = sid
        self.url = 'http://table.finance.yahoo.com/table.csv?s=%s.sz'
        self.url %= str(sid).rjust(6,'0')
        self.queue = queue

    def download(self,url):
        response = requests.get(url,timeout=3)
        if response.ok:
            return StringIO(response.content)

    def run(self):
        print('download',self.sid)
        # 1
        data = self.download(self.url)
        # 2 (sid,data)
        # lock
        self.queue.put((self.sid,data))

        
class ConvertThread(Thread,queue):
    def __init__(self):
        Thread.__init__(self)
        self.queue = queue

    def csvToxml(self,scsv,fxml):
        reader = csv.reader(scsv)
        header = reader.next()
        headers = map(lambda h: h.replace( , ),headers)
    
        root = Element("Data")
        for row in reader:
            eRow = Element("Row")
            root.append(eRow)
            for tag,text in zip(headers,row):
                e = Element(tag)
                e.text = text
                eRow.append(e)

        pretty(root)
        et = ElementTree(root)
        et.write(fxml)

    def run(self):
        #1 sid,data
        while True:
            sid,data = self.queue.get()
            print('Convert',sid)
            if sid == -1:
                break
            if data:
            fname = str(sid).rjust(6,'0') +'.xml'
            with open(fname,'wb') as wf:
                self.csvToxml(data,wf)

def handle(sid):
    print('Download...(%d)' % sid)
    url = 'http://table.finance.yahoo.com/table.csv?s=%s.sz'
    url %= str(sid).rjust(6,'0')
    rf = download(url)
    if rf is None:return

    print('convert to xml...(%d)' % sid)
    fname = str(sid).rjust(6,'0') +'.xml'
    with open(fname,'wb') as wf:
        csvToxml(rf,wf)

q = Queue()
dThreads = [DownloadThreadI(i,q) for i in xrange(1,11)]
cThread = ConvertThread(q)
for t in dThreads:
    t.start()
cThread.start()

for t in dThreads:
    t.join()

q.put((-1,None))

==============================================================================================
import requests
import base64
from io import StringIO
import csv
from xml.etree.ElementTree import ElementTree, Element, SubElement
from threading import Thread

apikey = 'OjZlY2MzYTQwNGVlMTI3Y2VkYjMyYTZiNzJiYzdlOTFk'

class DownloadThread(Thread):
    def __init__(self, page_number,queue):
        super().__init__()
        self.page_number = page_number
        self.queue = queue

    def run(self):
        csv_file = None
        while not csv_file:
            csv_file = self.download_csv(self.page_number)
        self.queue.put((self.page_number,csv_file))

    def download_csv(self,page_number):
        print('download csv data [page=%s]' % page_number)
        url = "https://api.intrinio.com/prices.csv?api_key=OjZlY2MzYTQwNGVlMTI3Y2VkYjMyYTZiNzJiYzdlOTFk&identifier=AAPL&page_size=20&page_number=%s&start_date=2017-09-28&end_date=2020-09-28" % page_number
        # auth = b'Basic ' + base64.b64encode(b'%s' % api_key)
        # headers = {'Authorization' : auth}
        response = requests.get(url)

        if response.ok:
            return StringIO(response.text)

class ConvertThread(Thread):
    def __init__(self,queue):
        super().__init__()
        self.queue = queue

    def run(self):
        while True:
            page_number,csv_file = self.queue.get()
            if page_number == -1:
                break
            self.csv_to_xml(csv_file,'data%s.xml' % page_number)

    def csv_to_xml(self,csv_file, xml_path):
        print('Convert csv data to %s' % xml_path)
        reader = csv.reader(csv_file)
        headers = next(reader)

        root = Element('Data')
        root.text = '\n\t'
        root.tail = '\n'

        for row in reader:
            book = SubElement(root, 'Row')
            book.text = '\n\t\t'
            book.tail = '\n\t'

            for tag, text in zip(headers, row):
                e = SubElement(book, tag)
                e.text = text
                e.tail = '\n\t\t'
            e.tail = '\n\t'

        ElementTree(root).write(xml_path, encoding='utf8')

# def download_and_save(page_number, xml_path):
    # # IO
    # csv_file = None
    # while not csv_file:
        # csv_file = download_csv(page_number)
    # # CPU
    # csv_to_xml(csv_file, 'data%s.xml' % page_number)

# class MyThread(Thread):
    # def __init__(self, page_number, xml_path):
        # super().__init__()
        # self.page_number = page_number
        # self.xml_path = xml_path
# 
    # def run(self):
        # download_and_save(self.page_number, self.xml_path)

from queue import Queue  # 这个队列是自动有锁的，遵循先进先出原则，队列属于临界区，如果不加锁，多个线程同时操作容易出问题。线程安全。

if __name__ == '__main__':
    queue = Queue()
    import time
    t0 = time.time()
    thread_list = []
    for i in range(1, 6):
        t = DownloadThread(i,queue)
        t.start()
        thread_list.append(t)

    convert_thread= ConvertThread(queue)
    convert_thread.start()

    for t in thread_list:
        t.join()
    # for i in range(1, 6):
    #      download_and_save(i, 'data%s.xml' % i)
    print(time.time() - t0)
    print('main thread end.')
    queue.put((-1,None))  # 让自动跳出死循环

GIL说明：