Completer Example

The Completer example shows how to provide string-completion facilities for an input widget based on data provided by a model.


This example uses a custom item model, FileSystemModel, and a QCompleter object. QCompleter is a class that provides completions based on an item model. The type of model, the completion mode, and the case sensitivity can be selected using combo boxes.

The Resource File

The Completer example requires a resource file in order to store the countries.txt and words.txt. The resource file contains the following code:

<Code snippet "/tmp/snapshot-qt5full-6.2/qt5/qtbase/tools/completer/completer.qrc" not found>

FileSystemModel Class Definition

The FileSystemModel class is a subclass of QFileSystemModel , which provides a data model for the local filesystem.

class FileSystemModel(QFileSystemModel):

# public
    FileSystemModel(QObject parent = None)
    data = QVariant(QModelIndex index, int role = Qt.DisplayRole)

This class only has a constructor and a data() function as it is only created to enable data() to return the entire file path for the display role, unlike QFileSystemModel ‘s data() function that only returns the folder and not the drive label. This is further explained in FileSystemModel's implementation.

FileSystemModel Class Implementation

The constructor for the FileSystemModel class is used to pass parent to QFileSystemModel .

def __init__(self, parent):
    QFileSystemModel.__init__(self, parent)

As mentioned earlier, the data() function is reimplemented in order to get it to return the entire file parth for the display role. For example, with a QFileSystemModel , you will see “Program Files” in the view. However, with FileSystemModel, you will see “C:\Program Files”.

def data(self, QModelIndex index, int role):

    if (role == Qt.DisplayRole and index.column() == 0) {
        path = QDir.toNativeSeparators(filePath(index))
        if (path.endsWith(QDir.separator()))
        return path

    return, role)

The EditRole , which QCompleter uses to look for matches, is left unchanged.

MainWindow Class Definition

The MainWindow class is a subclass of QMainWindow and implements five private slots - about(), changeCase(), changeMode(), changeModel(), and changeMaxVisible().

class MainWindow(QMainWindow):

# public
    MainWindow(QWidget parent = None)
slots: = private()
    def about():
    def changeCase(int):
    def changeMode(int):
    def changeModel():
    def changeMaxVisible(int):

Within the MainWindow class, we have two private functions: createMenu() and modelFromFile(). We also declare the private widgets needed - three QComboBox objects, a QCheckBox , a QCompleter , a QLabel , and a QLineEdit .

# private
    def createMenu():
    modelFromFile = QAbstractItemModel(QString fileName)
    caseCombo = None()
    modeCombo = None()
    modelCombo = None()
    maxVisibleSpinBox = None()
    wrapCheckBox = None()
    completer = None()
    contentsLabel = None()
    lineEdit = None()

MainWindow Class Implementation

The constructor of MainWindow constructs a MainWindow with a parent widget and initializes the private members. The createMenu() function is then invoked.

We set up three QComboBox objects, modelComb, modeCombo and caseCombo. By default, the modelCombo is set to QFileSystemModel , the modeCombo is set to “Filtered Popup” and the caseCombo is set to “Case Insensitive”.

def __init__(self, parent):
    QMainWindow.__init__(self, parent)

    centralWidget = QWidget()
    modelLabel = QLabel()
    modelCombo = QComboBox
    modelCombo.addItem(tr("QFileSystemModel that shows full path"))
    modelCombo.addItem(tr("Country list"))
    modelCombo.addItem(tr("Word list"))
    modeLabel = QLabel()
    modeLabel.setText(tr("Completion Mode"))
    modeCombo = QComboBox
    modeCombo.addItem(tr("Filtered Popup"))
    modeCombo.addItem(tr("Unfiltered Popup"))
    caseLabel = QLabel()
    caseLabel.setText(tr("Case Sensitivity"))
    caseCombo = QComboBox
    caseCombo.addItem(tr("Case Insensitive"))
    caseCombo.addItem(tr("Case Sensitive"))

The maxVisibleSpinBox is created and determines the number of visible item in the completer

The wrapCheckBox is then set up. This checkBox determines if the completer's setWrapAround() property is enabled or disabled.

maxVisibleLabel = QLabel()
maxVisibleLabel.setText(tr("Max Visible Items"))
maxVisibleSpinBox = QSpinBox
wrapCheckBox = QCheckBox
wrapCheckBox.setText(tr("Wrap around completions"))

We instantiate contentsLabel and set its size policy to fixed . The combo boxes’ activated() signals are then connected to their respective slots.

contentsLabel = QLabel
contentsLabel.setSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed)
connect(modelCombo, QComboBox.activated,
        self, MainWindow::changeModel)
connect(modeCombo, QComboBox.activated,
        self, MainWindow::changeMode)
connect(caseCombo, QComboBox.activated,
        self, MainWindow::changeCase)
connect(maxVisibleSpinBox, QSpinBox.valueChanged,
        self, MainWindow::changeMaxVisible)

The lineEdit is set up and then we arrange all the widgets using a QGridLayout . The changeModel() function is called, to initialize the completer.

lineEdit = QLineEdit
layout = QGridLayout()
layout.addWidget(modelLabel, 0, 0); layout.addWidget(modelCombo, 0, 1)
layout.addWidget(modeLabel, 1, 0); layout.addWidget(modeCombo, 1, 1)
layout.addWidget(caseLabel, 2, 0); layout.addWidget(caseCombo, 2, 1)
layout.addWidget(maxVisibleLabel, 3, 0); layout.addWidget(maxVisibleSpinBox, 3, 1)
layout.addWidget(wrapCheckBox, 4, 0)
layout.addWidget(contentsLabel, 5, 0, 1, 2)
layout.addWidget(lineEdit, 6, 0, 1, 2)

The createMenu() function is used to instantiate the QAction objects needed to fill the fileMenu and helpMenu. The actions’ triggered() signals are connected to their respective slots.

def createMenu(self):

    exitAction = QAction(tr("Exit"), self)
    aboutAct = QAction(tr("About"), self)
    aboutQtAct = QAction(tr("About Qt"), self)
    connect(exitAction, QAction.triggered, qApp, QApplication.quit)
    connect(aboutAct, QAction.triggered, self, MainWindow.about)
    connect(aboutQtAct, QAction.triggered, qApp, QApplication.aboutQt)
    fileMenu = menuBar().addMenu(tr("File"))
    helpMenu = menuBar().addMenu(tr("About"))

The modelFromFile() function accepts the fileName of a file and processes it depending on its contents.

We first validate the file to ensure that it can be opened in QFile::ReadOnly mode. If this is unsuccessful, the function returns an empty QStringListModel .

MainWindow::modelFromFile = QAbstractItemModel(QString fileName)

    file = QFile(fileName)
    if (not
        def QStringListModel(completer):

The mouse cursor is then overridden with WaitCursor before we fill a QStringList object, words, with the contents of file. Once this is done, we restore the mouse cursor.

#ifndef QT_NO_CURSOR
    words = QStringList()
    while (not file.atEnd()) {
        line = file.readLine()
        if (not line.isEmpty())
            words << QString.fromUtf8(line.trimmed())

#ifndef QT_NO_CURSOR

As mentioned earlier, the resources file contains two files - countries.txt and words.txt. If the file read is words.txt, we return a QStringListModel with words as its QStringList and completer as its parent.

if (not fileName.contains("countries.txt"))
    def QStringListModel(words,completer):

If the file read is countries.txt, then we require a QStandardItemModel with words.count() rows, 2 columns, and completer as its parent.

m = QStandardItemModel(words.count(), 2, completer)

A standard line in countries.txt is:

Norway NO

Hence, to populate the QStandardItemModel object, m, we have to split the country name and its symbol. Once this is done, we return m.

for i in range(0, words.count()):
    countryIdx = m.index(i, 0)
    symbolIdx = m.index(i, 1)
    country =, words[i].length() - 2).trimmed()
    symbol =
    m.setData(countryIdx, country)
    m.setData(symbolIdx, symbol)

return m

The changeMode() function sets the completer's mode, depending on the value of index.

def changeMode(self, index):

    QCompleter.CompletionMode mode
    if (index == 0)
        mode = QCompleter.InlineCompletion
    elif index == 1:
        mode = QCompleter.PopupCompletion
        mode = QCompleter.UnfilteredPopupCompletion

The changeModel() function changes the item model used based on the model selected by the user.

A switch statement is used to change the item model based on the index of modelCombo. If case is 0, we use an unsorted QFileSystemModel , providing us with a file path excluding the drive label.

def changeModel(self):

    del completer
    completer = QCompleter(self)
    switch (modelCombo.currentIndex()) {
    case 0:
        { // Unsorted QFileSystemModel
            fsModel = QFileSystemModel(completer)
            contentsLabel.setText(tr("Enter file path"))


Note that we create the model with completer as the parent as this allows us to replace the model with a new model. The completer will ensure that the old one is deleted the moment a new model is assigned to it.

If case is 1, we use the DirModel we defined earlier, resulting in full paths for the files.

case 1:
    { // FileSystemModel that shows full paths
        fsModel = FileSystemModel(completer)
        contentsLabel.setText(tr("Enter file path"))


When case is 2, we attempt to complete names of countries. This requires a QTreeView object, treeView. The country names are extracted from countries.txt and set the popup used to display completions to treeView.

case 2:
    { // Country List
        treeView = QTreeView()
        treeView.header().setSectionResizeMode(0, QHeaderView.Stretch)
        treeView.header().setSectionResizeMode(1, QHeaderView.ResizeToContents)
        contentsLabel.setText(tr("Enter name of your country"))


The screenshot below shows the Completer with the country list model.


If case is 3, we attempt to complete words. This is done using a QStringListModel that contains data extracted from words.txt. The model is sorted case insensitively .

The screenshot below shows the Completer with the word list model.


Once the model type is selected, we call the changeMode() function and the changeCase() function and set the wrap option accordingly. The wrapCheckBox's clicked() signal is connected to the completer's setWrapAround() slot.

case 3:
    { // Word list
        contentsLabel.setText(tr("Enter a word"))


connect(wrapCheckBox, QAbstractButton.clicked, completer, QCompleter.setWrapAround)

The changeMaxVisible() update the maximum number of visible items in the completer.

def changeMaxVisible(self, max):


The about() function provides a brief description about the example.

def about(self):

    QMessageBox.about(self, tr("About"), tr("This example demonstrates the "
        "different features of the QCompleter class."))

`` main()``


The main() function instantiates QApplication and MainWindow and invokes the show() function.

if __name__ == "__main__":

    app = QApplication([])
    window = MainWindow()

Example project @