为什么QtNetwork.QFtp.get下载在多个文件的for循环中失败？
为什么QtNetwork.QFtp.get下载在多个文件的for循环中失败？
提问于 2016-12-27 18:48:13
我正在尝试使用for循环从ftp站点下载多个文件。在弹出python.exe关闭窗口之前，以下代码似乎只适用于循环中的前2个文件。两个下载的文件是完美的，但第三个下载的文件在关机时是空的。剩下的文件我都搞不懂。你知道问题出在哪里吗？
from PyQt4 import QtCore, QtGui, QtNetwork
class FtpWindow(QtGui.QDialog):
def __init__(self, parent=None):
self.fileList = QtGui.QTreeWidget()
self.ftp = QtNetwork.QFtp(self)
self.progressDialog = QtGui.QProgressDialog(self)
self.downloadAllButton.clicked.connect(self.downloadAllFile)
self.ftp.commandFinished.connect(self.ftpCommandFinished)
def downloadAllFile(self):
for jj in range(self.fileList.topLevelItemCount()): # how many files in a particular folder
fileName = self.fileList.topLevelItem(jj).text(0)
self.outFile = QtCore.QFile(fileName)
self.ftp.get(fileName, self.outFile) #download one file at a time
self.progressDialog.setLabelText("Downloading %s..." % fileName)
self.progressDialog.exec_()
def ftpCommandFinished(self, _, error):
self.setCursor(QtCore.Qt.ArrowCursor)
if self.ftp.currentCommand() == QtNetwork.QFtp.Get:
if error:
self.statusLabel.setText("Canceled download of %s." % self.outFile.fileName())
self.outFile.close()
self.outFile.remove()
else:
self.statusLabel.setText("Downloaded %s to current directory." % self.outFile.fileName())
self.outFile.close()
self.outFile = None
self.enableDownloadButton()
self.progressDialog.hide()回答 2
Stack Overflow用户
发布于 2017-01-03 11:05:39
self.progressDialog.exec_()应该是阻塞模式对话框。对非阻塞调用使用self.progressDialog.show()。
看起来ftp get是非阻塞的，所以您必须等待，直到使用commandFinished()信号完成下载。
我的猜测是，循环中的每个迭代都会覆盖self.outFile，因此没有任何python对对象的引用。这使得对象在python执行垃圾回收时就会死掉。我的猜测是，前两个文件较小且快速，第三个文件较大，因此其他文件可以在垃圾回收之前下载。对于最后一个文件，要么是垃圾收集，要么是更快。
http://pyside.github.io/docs/pyside/PySide/QtNetwork/QFtp.html#PySide.QtNetwork.PySide.QtNetwork.QFtp.get
class FtpWindow(QtGui.QDialog):
def __init__(self, parent=None):
self.fileList = QtGui.QTreeWidget()
self.ftp = QtNetwork.QFtp(self)
self.progressDialog = QtGui.QProgressDialog(self)
self.progressDialog.canceled.connect(self.ftp.abort)
self.downloadAllButton.clicked.connect(self.downloadAllFile)
self.ref_holder = {}
self.ftp.commandFinished.connect(self.ftpCommandFinished)
def download_file(self, filename):
"""Non blocking start downloading a file."""
outFile = QtCore.QFile(filename)
cmd_id = self.ftp.get(filename, outFile) # Non blocking just start downloading
# This keeps the object alive and doesn't overwrite them.
self.ref_holder[cmd_id] = [filename, outFile]
def downloadAllFile(self):
self.progressDialog.reset()
num_downloads = self.fileList.topLevelItemCount()
self.progressDialog.setMaximum(num_downloads)
self.progressDialog.setValue(0)
self.progressDialog.setLabelText("Downloading %d files ..." % num_downloads)
self.progressDialog.show()
for jj in range(num_downloads): # how many files in a particular folder
fileName = self.fileList.topLevelItem(jj).text(0)
self.download_file(fileName) # Non blocking, and doesn't overwrite self.outFile with every iteration
def ftpCommandFinished(self, cmd_id, error=None):
"""Increased the number of items finished."""
self.progressDialog.setValue(self.progressDialog.value()+1)
item = self.ref_holder.pop(cmd_id) # Remove the reference for the finished item
if error:
self.progressDialog.setLabelText("Error downloading %s" % item[0])
# Check if all downloads are done
if len(self.ref_holder) == 0:
self.progressDialog.setValue(self.progressDialog.maximium())
self.progressDialog.close() # This shouldn't be needed我上面的示例将保留文件名和outFile对象引用，直到命令结束。当命令结束时，引用被删除，允许python清理对象。
Stack Overflow用户
发布于 2017-01-04 06:34:22
感谢HashSplat的输入。我有一些更新，使其功能齐全：
class FtpWindow(QtGui.QDialog):
def __init__(self, parent=None):
self.fileList = QtGui.QTreeWidget()
self.ftp = QtNetwork.QFtp(self)
self.progressDialog = QtGui.QProgressDialog(self)
self.progressDialog.canceled.connect(self.ftp.abort)
self.downloadAllButton.clicked.connect(self.downloadAllFile)
self.ref_holder = {}
self.ftp.commandFinished.connect(self.ftpCommandFinished)
def download_file(self, fileName):
"""Non blocking start downloading a file."""
self.outFile = QtCore.QFile(fileName)
""" Need this to have files saved locally """
if not self.outFile.open(QtCore.QIODevice.WriteOnly):
QtGui.QMessageBox.information(self, "FTP",
"Unable to save the file %s." % fileName)
self.outFile = None
return
cmd_id = self.ftp.get(filename, self.outFile) # Non blocking just start downloading
# This keeps the object alive and doesn't overwrite them.
self.ref_holder[cmd_id] = [filename, self.outFile]
def downloadAllFile(self):
self.progressDialog.reset()
self.num_downloads = self.fileList.topLevelItemCount()
self.counter=1
self.progressDialog.setLabelText("Downloading %d/%d files ..." % (self.counter, self.num_downloads))
self.progressDialog.show()
for jj in range(num_downloads): # how many files in a particular folder
fileName = self.fileList.topLevelItem(jj).text(0)
self.download_file(fileName) # Non blocking, and doesn't overwrite self.outFile with every iteration
def ftpCommandFinished(self, cmd_id, error=None):
"""Increased the number of items finished."""
self.progressDialog.setValue(self.progressDialog.value()+1)
item = self.ref_holder.pop(cmd_id) # Remove the reference for the finished item
if error:
self.progressDialog.setLabelText("Error downloading %s" % item[0])
# Check if all downloads are done
if len(self.ref_holder) == 0:
self.progressDialog.close() # This closes the extra window
self.outFile.close() # You need this to have the last file saved
else:
self.counter+=1
self.progressDialog.setLabelText("Downloading %d/%d files ..." % (self.counter, self.num_downloads))
def updateDataTransferProgress(self, readBytes, totalBytes):
self.progressDialog.setMaximum(totalBytes)
self.progressDialog.setValue(readBytes)页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/41343698
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