我从这里开始一个新的话题,它将与
this question
.
我邀请你们只是在背景下阅读,以获得全球的想法。
因此,我有一个下载函数,它依赖于python 3.2 API(由私人公司开发)。每个文件最多需要400秒。
显然,我并不是只有一个文件可以下载,所以我已经尝试了好几天把每个下载过程放在一个线程池中。池中的每个线程都应该完全独立于GUI主线程。当其中一个完成后,它应该只向GUI发送一个信号。
我做了几次测试,但不管使用什么技术,但是
-
GUI冻结;
-
结果仅在所有线程的处理结束时给出,而不是一个接一个地给出。
我认为API提供的下载方法是一个无法线程化的阻塞函数。
所以我的问题很简单:如何知道一个I/O方法是否可以通过线程处理。
2017年11月24日更新
任务的结果仅在全局处理结束时给出(行为映射异步)。这不是我想要的。我希望插入更多的实时信息,并立即在控制台上查看每个已完成任务的消息。
import time
import multiprocessing
import private.library as bathy
from PyQt4 import QtCore, QtGui
import os
import sys
user = 'user'
password = 'password'
server = 'server'
basename = 'basename'
workers = multiprocessing.cpu_count()
node = bathy.NodeManager(user, password, server)
database = node.get_database(basename)
ids = (10547, 3071, 13845, 13846, 13851, 13844, 5639, 4612, 4613, 954,
961, 962, 4619, 4620, 4622, 4623, 4624, 4627, 4628, 4631,
4632, 4634, 4635, 4638, 4639, 4640, 4641, 4642, 10722, 1300,
1301, 1303, 1310, 1319, 1316, 1318, 1321, 1322, 1323, 1324,
1325, 1347, 1348, 1013, 1015, 1320, 8285, 8286, 8287, 10329,
9239, 9039, 5006, 5009, 5011, 5012, 5013, 5014, 5015, 5025,
5026, 4998, 5040, 5041, 5042, 5043, 11811, 2463, 2464, 5045,
5046, 5047, 5048, 5049, 5053, 5060, 5064, 5065, 5068, 5069,
5071, 5072, 5075, 5076, 5077, 5079, 5080, 5081, 5082, 5083,
5084, 5085, 5086, 5087, 5088, 5090, 5091, 5092, 5093)
# ---------------------------------------------------------------------------------
def download(surface_id, index):
global node
global database
t = time.time()
message = 'Surface #%d - Process started\n' % index
surface = database.get_surface(surface_id)
metadata = surface.get_metadata()
file_path = os.path.join("C:\\Users\\philippe\\Test_Download",
metadata["OBJNAM"] + ".surf")
try:
surface.download_bathymetry(file_path)
except RuntimeError as error:
message += "Error : " + str(error).split('\n')[0] + '\n'
finally:
message += ('Process ended : %.2f s\n' % (time.time() - t))
return message
# ---------------------------------------------------------------------------------
def pass_args(args):
# Method to pass multiple arguments to download (multiprocessing.Pool)
return download(*args)
# ---------------------------------------------------------------------------------
class Console(QtGui.QDialog):
def __init__(self):
super(self.__class__, self).__init__()
self.resize(600, 300)
self.setMinimumSize(QtCore.QSize(600, 300))
self.setWindowTitle("Console")
self.setModal(True)
self.verticalLayout = QtGui.QVBoxLayout(self)
# Text edit
# -------------------------------------------------------------------------
self.text_edit = QtGui.QPlainTextEdit(self)
self.text_edit.setReadOnly(True)
self.text_edit_cursor = QtGui.QTextCursor(self.text_edit.document())
self.verticalLayout.addWidget(self.text_edit)
# Ok / Close
# -------------------------------------------------------------------------
self.button_box = QtGui.QDialogButtonBox(self)
self.button_box.setStandardButtons(QtGui.QDialogButtonBox.Close |
QtGui.QDialogButtonBox.Ok)
self.button_box.setObjectName("button_box")
self.verticalLayout.addWidget(self.button_box)
# Connect definition
# -------------------------------------------------------------------------
self.connect(self.button_box.button(QtGui.QDialogButtonBox.Close),
QtCore.SIGNAL('clicked()'),
self.button_cancel_clicked)
self.connect(self.button_box.button(QtGui.QDialogButtonBox.Ok),
QtCore.SIGNAL('clicked()'),
self.button_ok_clicked)
# Post initialization
# -------------------------------------------------------------------------
self.pool = multiprocessing.Pool(processes=workers)
# Connect functions
# -----------------------------------------------------------------------------
def button_cancel_clicked(self):
self.close()
def button_ok_clicked(self):
jobs_args = [(surface_id, index) for index, surface_id in enumerate(ids)]
async = pool.map_async(pass_args, jobs_args)
pool.close()
# Busy waiting loop
while True:
# pool.map_async has a _number_left attribute, and a ready() method
if async.ready():
self.write_stream("All tasks completed\n")
pool.join()
for line in async.get():
self.write_stream(line)
break
remaining = async._number_left
self.write_stream("Waiting for %d task(s) to complete...\n" % remaining)
time.sleep(0.5)
# Other functions
# -----------------------------------------------------------------------------
def write_stream(self, text):
self.text_edit.insertPlainText(text)
cursor = self.text_edit.textCursor()
self.text_edit.setTextCursor(cursor)
app.processEvents()
# ---------------------------------------------------------------------------------
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
window = Console()
window.show()
app.exec_()
问题
-
乍一看,上面的代码是否存在概念错误?
-
在这种特定情况下,我必须使用apply\u async方法才能获得更具交互性的东西吗?
-
你能指导我如何使用回调函数发布自定义事件来更新控制台(方法由@ekhumoro提出)吗?
2017年11月25日更新
我尝试了apply\u async:
def button_ok_clicked(self):
# Pool.apply_async - the call returns immediately instead of
# waiting for the result
for index, surface_id in enumerate(ids):
async = pool.apply_async(download,
args=(surface_id, index),
callback=self.write_stream)
pool.close()
通过回调:
def write_stream(self, text):
# This is called whenever pool.apply_async(i) returns a result
self.text_edit.insertPlainText(text)
cursor = self.text_edit.textCursor()
self.text_edit.setTextCursor(cursor)
# Update the text edit
app.processEvents()
不幸的是,这样做会导致应用程序崩溃。我认为我必须设置一个锁定机制,以防止所有任务同时在文本编辑中写入。
