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pythonpyqt5qlineedit

Why does a QLineEdit widget generate an "editingFinished" signal when other widgets are activated?

I'm trying to understand why QLineEdit "editingFinished" signals are generated when other widgets are selected. In the example below the "on_lineedit" method is called when the combo box is selected. Why?

ui example

import sys
from PyQt5 import QtWidgets

class MyApp(QtWidgets.QDialog):
    def __init__(self, *args):
        super().__init__(*args)
        # create combobox:
        combobox = QtWidgets.QComboBox(self)
        combobox.addItems(['Item 1', 'Item 2'])
        # create line edit
        lineedit = QtWidgets.QLineEdit(self)
        lineedit.editingFinished.connect(self.on_lineedit)
        # layout:
        vbox = QtWidgets.QVBoxLayout()
        vbox.addWidget( combobox )
        vbox.addWidget( lineedit )
        self.setLayout(vbox)

    def on_lineedit(self):
        print('on_lineedit')

app    = QtWidgets.QApplication(sys.argv)
window = MyApp()
window.show()
sys.exit(app.exec_())

I know that this issue can be avoided by connecting the "textChanged" signal instead of the "editingFinished" signal like this:

lineedit.textChanged.connect(self.on_lineedit)

and I've seen similar issues raised elsewhere (links below) but I still don't understand why the "editingFinished" signal is generated when the combobox is selected.

Qt qspinbox editingFinished signal on value changed

Suppress QLineEdit editingFinished signal when certain button is clicked

Solution

  • From http://doc.qt.io/archives/qt-4.8/qlineedit.html#editingFinished

    This signal is emitted when the Return or Enter key is pressed or the line edit loses focus.

    The signal is emitted because it is designed to be. The other widget your click on is not really relevant here, what is relevant is that it the line edit loses focus and it is that which causes the signal to be emitted. Clicking on another widget is just one of many ways your line edit might lose focus.