📄 index.lxp@lxpwrap=x945_252ehtm.htm
字号:
<table border="0" cellspacing="0" cellpadding="3" width="100%"><tr><td> <div align="center" id="bldcontent"> <a href="../default.htm"><img src="../images/opendocs.png" width="63" height="76" border="0"></a> <br> <div class="symbol">Your OpenSource Publisher™</div> </div> </td></tr></table> <div align="center" class="author"> <a href="../products.lxp">Products</a> | <a href="../wheretobuy.lxp">Where to buy</a> | <a href="../bookstore.lxp">Retailers</a> | <a href="../faq.lxp">FAQ</a> | <a href="../writeforus.lxp">Write for Us.</a> | <a href="#contact">Contact Us.</a> </div> <table border="0" cellspacing="3" cellpadding="0" width="100%"><tr><td width="100%"> <div class="content"> <table border="0" cellspacing="2" cellpadding="0" width="100%"><tr><td width="100%"> <div align="center"><H4 CLASS="AUTHOR"><A NAME="AEN5">Boudewijn Rempt</A><br><a href="../../https@secure.linuxports.com/opendocs/default.htm"><img src=odpyqt125.png></a><br>ISBN: 0-97003300-4-4<br><a href="../../https@secure.linuxports.com/opendocs/default.htm">Available from bookstores everywhere or you can order it here.</a><p>You can download the source files for the book <a href="pyqtsrc.tgz">(code / eps) here.</a><hr></div> <HTML><HEAD><TITLE>Setting breakpoints</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.72"><LINKREL="HOME"TITLE="GUI Programming with Python: QT Edition"HREF="book1.htm"><LINKREL="UP"TITLE="Debugging"HREF="c883.htm"><LINKREL="PREVIOUS"TITLE="Debugging"HREF="c883.htm"><LINKREL="NEXT"TITLE="Stepping along"HREF="x966.htm"></HEAD><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#0000FF"VLINK="#840084"ALINK="#0000FF"><DIVCLASS="NAVHEADER"><TABLESUMMARY="Header navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">GUI Programming with Python: QT Edition</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><A accesskey="P" href="index.lxp@lxpwrap=c883_252ehtm.htm">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">Chapter 5. Debugging</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><A accesskey="N" href="index.lxp@lxpwrap=x966_252ehtm.htm">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1">Setting breakpoints</A></H1><P>Setting a breakpoint in your script is done by clicking on the left vertical gray bar in the editor pane. It will place a small, inconspicuous white circle in the editor border. You can also set and unset breakpoints during a debugging session.</P><DIVCLASS="MEDIAOBJECT"><P><DIVCLASS="CAPTION"><P>Setting a breakpoint (the small white circle left to ‘print i').</P></DIV></P></DIV><P>Now, if you start debugging the script, and press the Continue button, the script will run until it arrives at the <TTCLASS="LITERAL">print i</TT> line. The output will show up in the Python Interpreter window, if you have it open.</P><P>Now that you know how breakpoints work, I'll show a good way to use them.</P><P>In GUI programming, breakpoints are often the only way of debugging code that becomes activated after the main loop has started. Let's look at the following script, where there is a bug in the code that is activated when the button is pressed:</P><PRECLASS="PROGRAMLISTING">## button.py#from qt import *import sysclass MainWindow(QMainWindow): def __init__(self, *args): apply(QMainWindow.__init__, (self,) + args) self.setCaption("Button") self.grid=QGrid(2, self) self.grid.setFrameShape(QFrame.StyledPanel) self.bn=QPushButton("Hello World", self.grid) self.bn.setDefault(1) self.connect(self.bn, SIGNAL("clicked()"), self.slotSlot) self.setCentralWidget(self.grid) def slotSlot(self): i = 1/0def main(args): app=QApplication(args) win=MainWindow() win.show() app.connect(app, SIGNAL("lastWindowClosed()"), app, SLOT("quit()")) app.exec_loop()if __name__=="__main__": main(sys.argv) </PRE><P>If you try to single-step until you've arrived at the bug, you will be stepping for a long time. It is easier to continue the application until it hits the breakpoint in <TTCLASS="FUNCTION">slotSlot()</TT>, and take it from there by hand.</P></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLESUMMARY="Footer navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><A accesskey="P" href="index.lxp@lxpwrap=c883_252ehtm.htm">Prev</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><A accesskey="H" href="index.lxp@lxpwrap=book1_252ehtm">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><A accesskey="N" href="index.lxp@lxpwrap=x966_252ehtm.htm">Next</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">Debugging</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><A accesskey="U" href="index.lxp@lxpwrap=c883_252ehtm.htm">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">Stepping along</TD></TR></TABLE></DIV></BODY></HTML> </td> </tr> </table> </td> </tr> </table> ⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -