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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">this might help, I wrote it some time ago as a reminder to myself :)</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">http://python-camelot.s3.amazonaws.com/gpl/release/pyqt/doc/advanced/development.html</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">On Friday, September 20, 2013 09:50:25 PM Chris O'Halloran wrote:<br /></p>
<p style=" margin-top:12px; margin-bottom:0px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Hello all,<br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">This question will hopefully be trivial but I seem to have a mental block.<br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">I'm currently working through Jan Bodnar's Advanced PyQt tutorial and Mark Summerfield's Rapid Gui Application Development with Python and PyQt. Both paid for copies. Thanks guys if you're on this list!<br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">I'm a novice programmer but am making reasonable progress and have worked out how to embed Matplotlib graphs within PyQt windows and use dials and sliders to manipulate the maths in the graphs. Largely through copy and modifying others code.<br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">I'm now starting to explore the toolkit beyond the tutorials - although I haven't finished either of the works mentioned in the previous paragraph.<br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">But whenever I read the PyQt documentation the following is never clear to me.<br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">This is an example from.<br /><br /><a href="http://pyqt.sourceforge.net/Docs/PyQt4/qpushbutton.html"><span style=" text-decoration: underline; color:#0000c0;">http://pyqt.sourceforge.net/Docs/PyQt4/qpushbutton.html</span></a><br /><br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Say I'm wanting to make a button.<br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><br /><quote><br /></p>
<p style=" margin-top:16px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><span style=" font-size:x-large; font-weight:600;">Method Documentation</span></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">....<br /></p>
<p style=" margin-top:14px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><a name="QPushButton-2"></a><span style=" font-size:large; font-weight:600;">Q</span><span style=" font-size:large; font-weight:600;">PushButton.__init__ (</span><span style=" font-size:large; font-weight:600; font-style:italic;">self</span><span style=" font-size:large; font-weight:600;">, QString </span><span style=" font-size:large; font-weight:600; font-style:italic;">text</span><span style=" font-size:large; font-weight:600;">, QWidget</span><span style=" font-size:large; font-weight:600;"> </span><span style=" font-size:large; font-weight:600; font-style:italic;">parent</span><span style=" font-size:large; font-weight:600;"> = None)</span></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">The <span style=" font-style:italic;">parent</span> argument, if not None, causes <span style=" font-style:italic;">self</span> to be owned by Qt instead of PyQt.</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Constructs a push button with the parent <span style=" font-style:italic;">parent</span> and the text <span style=" font-style:italic;">text</span>.</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"></quote><br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><code></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">from PyQt4 import QtGui<br /><br />class Pluto(QtGui.QWidget):<br /> def __init__(self):<br /> super(Pluto, self).__init__()<br /> <br /> self.move(300,300)<br /> self.setWindowTitle("Size policy")<br /> <br /> self.initUI()<br /> <br /> def initUI(self):<br /> <br /> btn1 = QtGui.QPushButton("Button",self)<br /> btn1.setSizePolicy(QtGui.QSizePolicy.Fixed, QtGui.QSizePolicy.Fixed)<br /> <br /> btn2 = QtGui.QPushButton("Button2",self)<br /> <br /></p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"></code></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Now consider</p>
<p style=" margin-top:14px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><a name="QPushButton-2"></a><span style=" font-size:large; font-weight:600;">Q</span><span style=" font-size:large; font-weight:600;">PushButton.__init__ (</span><span style=" font-size:large; font-weight:600; font-style:italic;">self</span><span style=" font-size:large; font-weight:600;">, QString </span><span style=" font-size:large; font-weight:600; font-style:italic;">text</span><span style=" font-size:large; font-weight:600;">, QWidget</span><span style=" font-size:large; font-weight:600;"> </span><span style=" font-size:large; font-weight:600; font-style:italic;">parent</span><span style=" font-size:large; font-weight:600;"> = None)</span></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">and</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">btn2 = QtGui.QPushButton("Button2",self)</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Obviously "Button" is text and can be a QString and self refers to the a QWidget</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">but I never quite figure out what parent=None means.</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Is "QWidget parent=None" all part of one argument?<br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">is parent a key word argument? Ie you can pass other parameter to parent and not just 'None'.<br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Is as simple as <span style=" font-weight:600;">self </span>ie the QWidget is simply the parent of the QPushButton so that when the QWidget is destroyed the QPushButton is too.<br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">How would you write parent=None?</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Would it be</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">btn2 = QtGui.QPushButton("Button2") <br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">or is it</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">btn2 = QtGui.QPushButton("Button2", parent=None) </p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">btn2 = QtGui.QPushButton("Button2", self, parent=None) </p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">And, if I write my code</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">btn2 = QtGui.QPushButton("Button2",self)</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">and <span style=" font-weight:600;">self </span>is the<span style=" font-weight:600;"> parent</span> argument, ie not None, then I then have no idea what <span style=" font-weight:600;">self</span> being owned by Qt instead of PyQt actually means.</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Given that my code is bog standard, it seems a little odd that tricky things are happening with my object being owned by Qt instead of PyQt.<br /></p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Does this matter or have I interpreted this all incorrectly?</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Thanks for your patience if you've read this far.</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Cheers and regards,</p>
<p style=" margin-top:12px; margin-bottom:12px; margin-left:40px; margin-right:40px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Chris O'Halloran<br /></p>
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