[PyQt] First bottom-up GUI, acting strange

[Demetrius Cassidy]

Looking over your code, I suspect the problem is with this line:

data = webPage.read(8192)
       if not data:
           break

Unless data is 0 or None, it will go into an infinite loop. From your 
description, it does not sound like it will ever return 0. It is also not 
good programming practice to write loops that are by nature always True. I 
suggest you use the total number of bytes instead as the condition for your 
loop, so after x amount of bytes is read or written, the loop finishes.

I also suggest making the download in a separate thread, to avoid locking up 
the GUI during long downloads (because the while loop is going to be using 
up all the CPU time for your app, without giving the Qt event loop a chance 
to run).

----- Original Message ----- 
From: "Nonyaz" <cheech at nonyaz.com>
To: <pyqt at riverbankcomputing.com>
Sent: Saturday, April 18, 2009 11:58 PM
Subject: [PyQt] First bottom-up GUI, acting strange


>I made an attempt to port over a little command line file DL script I
> wrote into a GUI as a practice working with PyQt.
> While I have seemingly achieved that goal, the resulting product is
> not acting as I suspected. When I start a download,
> the GUI will continue to update as long as I don't click it, as soon
> as I do, the OS throws up "Not Responding" in the
> title bar and the GUI no longer updates.  Even when I don't click it,
> I can tell somethings not right, the start button never
> releases, and the progress bar effects on vista are not apparent.
>
> Hopefully someone can point out to me what I'm doing wrong, I have a
> feeling its just bad event loop execution, although
> I'm not quite sure how I could rewrite it so it wouldn't have this 
> problem.
>
> import urllib, os, time, sys, win32con
> import win32clipboard as w
> from PyQt4.QtCore import *
> from PyQt4.QtGui import *
>
> class Window(QDialog):
>   def __init__(self, parent=None):
>       super(Window, self).__init__(parent)
>
>       self.lineedit = QLineEdit()
>       self.getclip = QCommandLinkButton("Poll Clipboard")
>       self.progbar = QProgressBar()
>       self.speed = QLabel()
>       self.status = QLabel()
>       self.startb = QPushButton("Start DL")
>
>       grid = QGridLayout()
>       buttlay = QHBoxLayout()
>       buttlay.addStretch()
>       buttlay.addWidget(self.startb)
>       grid.addWidget(self.lineedit,0,0)
>       grid.addWidget(self.getclip,0,1)
>       grid.addWidget(self.progbar,1,0,1,0)
>       grid.addWidget(self.status,3,0)
>       grid.addWidget(self.speed,3,1)
>       grid.addLayout(buttlay,4,1)
>       self.setLayout(grid)
>
>       self.setWindowTitle("Clipboard DL V.001")
>       self.lineedit.setText(getText())
>       self.lineedit.setMinimumSize(300,0)
>       self.startb.setMaximumSize(75,300)
>
>       self.connect(self.startb, SIGNAL("clicked()"),
>                    fileDL)
>       self.connect(self.getclip, SIGNAL("clicked()"),
>                    setClipText)
>
>
> class myURLOpener(urllib.FancyURLopener):
>   def http_error_206(self, url, fp, errcode, errmsg, headers, data=None):
>       print "I've been 206'd!"
>       pass
>
> def getText():
>   w.OpenClipboard()
>   try:
>       d = w.GetClipboardData(win32con.CF_TEXT)
>   except:
>       d = "None."
>   w.CloseClipboard()
>   if d[:7] != "http://":
>       d = "Clipboard does not contain a valid URL."
>   return d
>
> def fileDL():
>   loop = 1
>   existSize = 0
>   dlFile = getFilename()
>   url = str(daprog.lineedit.text())
>
>   myUrlclass = myURLOpener()
>   webPage = myUrlclass.open(url)
>   contentLength = int(webPage.headers['Content-Length'])
>
>   if os.path.exists(str(dlFile)):
>       outputFile = open(dlFile,"ab")
>       existSize = os.path.getsize(dlFile)
>
>       if existSize < contentLength:
>           webPage.close()
>           myUrlclass = None
>           myUrlclass = myURLOpener()
>           myUrlclass.addheader("Range","bytes=%s-" % (existSize))
>           webPage = myUrlclass.open(url)
>
>   else:
>       try:
>           outputFile = open(dlFile,"wb")
>       except:
>           os.mkdir(dldir+'/'+show)
>       outputFile = open(dlFile,"wb")
>       existSize = 0
>
>
>   if existSize == contentLength:
>       daprog.status.setText("All %s bytes already downloaded!\n" %
> (contentLength))
>       raw_input()
>       loop = 0
>   elif existSize == 0:
>       pass
>   elif existSize < contentLength:
>       daprog.status.setText("Resuming download....")
>
>   numBytes = existSize
>   daprog.status.setText("Download Started")
>   counterr = 0
>   while loop:
>       if counterr == 0:
>           intime = time.time()
> 
> daprog.progbar.setValue((float(numBytes)/float(contentLength)*100))
>       data = webPage.read(8192)
>       if not data:
>           break
>       outputFile.write(data)
>       numBytes += len(data)
>       if counterr == 10:
>           counterr = -1
>           outtime = time.time()
>           lab = "%.2f KB/s" % (((8192*10)/(outtime-intime))/1000)
>           daprog.speed.setText(lab)
>       counterr += 1
>
>
>   daprog.progbar.setValue(100)
>   daprog.status.setText("Done")
>   webPage.close()
>   outputFile.close()
>
>
>
> def getFilename():
>   hack_fin = 0
>   fname = ''
>   for x in str(daprog.lineedit.text())[::-1]:
>       if x == "/":
>           hack_fin = 1
>       if x != "/":
>           if hack_fin == 0:
>               fname += x
>   return fname[::-1]
>
> def setClipText():
>   daprog.lineedit.setText(getText())
>
>
> app = QApplication(sys.argv)
> daprog = Window()
> daprog.show()
> daprog.exec_()
>
>
> Thanks for your help,
> - Adam
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