'Re: [PyQt] What is difference between "partial" and "lambda" in'

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List:       pykde
Subject:    Re: [PyQt] What is difference between "partial" and "lambda" in
From:       Vincent Vande Vyvre <vincent.vandevyvre () swing ! be>
Date:       2011-08-28 15:39:13
Message-ID: 4E5A6121.7060201 () swing ! be
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    Le 28/08/11 15:11, bluekyu a &eacute;crit&nbsp;:
    <blockquote cite="mid:4E5A3E66.4040605@gmail.com" type="cite">Hello.
      I have a question about "partial" and "lambda" in connect slot.
      <br>
      <br>
      I learned that "partial" and "lambda" can have arguments in
      connect slot.
      <br>
      So, I usually use lambda function, however, it does not work well
      in some code.
      <br>
      <br>
      My example code:
      <br>
      --------------------------------------------
      <br>
      from PyQt4.QtCore import *
      <br>
      from PyQt4.QtGui import *
      <br>
      import sys
      <br>
      from functools import partial
      <br>
      <br>
      app = QApplication(sys.argv)
      <br>
      form = QDialog()
      <br>
      layout = QVBoxLayout()
      <br>
      <br>
      label = QLabel("Test")
      <br>
      layout.addWidget(label)
      <br>
      <br>
      stringList = ["ABC", "123", "XYZ", "789"]
      <br>
      for string in stringList:
      <br>
      &nbsp;&nbsp;&nbsp; button = QPushButton(string)
      <br>
      &nbsp;&nbsp;&nbsp; layout.addWidget(button)
      <br>
      &nbsp;&nbsp;&nbsp; form.connect(button, SIGNAL("clicked()"),
      <br>
      #&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \
lambda: label.setText(string))&nbsp;&nbsp;&nbsp; # Problem  <br>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \
partial(label.setText, string))  <br>
      <br>
      form.setLayout(layout)
      <br>
      form.show()
      <br>
      app.exec_()
      <br>
      ---------------------------------------------
      <br>
      <br>
      I expected that each button set label text as each string, but all
      button set label text as "789".
      <br>
      Instead, partial function works very well.
      <br>
      <br>
      What is difference between "partial" and "lambda"?
      <br>
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  <br>
      <br>
    </blockquote>
    Your's lambda function is not correct.<br>
    <br>
    Use this:<br>
    <br>
    &nbsp;&nbsp;&nbsp; form.connect(button, SIGNAL("clicked()"),<br>
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \
lambda s=string: label.setText(s))<br>  <br>
    <br>
    <br>
    <div class="moz-signature">-- <br>
      Vincent V.V.<br>
      <a href="https://launchpad.net/oqapy">Oqapy</a> . <a
        href="https://launchpad.net/qarte+7">Qarte+7</a> . <a
        href="https://launchpad.net/paqager">PaQager</a></div>
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