Tutorial on PyQt6 QTextEdit widget

The QTextEdit widget in PyQt6 provides a powerful multi-line text editor that supports plain text, rich text (HTML), and advanced formatting. It is commonly used for input fields, document editors, and text displays.

In this tutorial, we’ll cover:

1. Basics of QTextEdit

The QTextEdit widget is a multi-line text editor that can display or accept plain text and rich text.

Example: Basic QTextEdit Setup

from PyQt6.QtWidgets import QApplication, QMainWindow, QTextEdit

def main():
    app = QApplication([])
    window = QMainWindow()
    window.setWindowTitle("Basic QTextEdit Example")
    window.setGeometry(100, 100, 400, 300)

    text_edit = QTextEdit(window)
    text_edit.setGeometry(50, 50, 300, 200)

    window.show()
    app.exec()

if __name__ == "__main__":
    main()

Output:

• A window with a blank multi-line text editor.

2. Setting and Retrieving Text

You can use setText() to set the content and toPlainText() to retrieve plain text.

Example: Set and Get Plain Text

text_edit = QTextEdit(window)
text_edit.setGeometry(50, 50, 300, 200)

# Set text
text_edit.setText("Welcome to PyQt6 QTextEdit!")

# Get text
print(text_edit.toPlainText())

3. Rich Text and HTML

QTextEdit supports HTML for displaying rich text.

Example: Setting Rich Text

text_edit = QTextEdit(window)
text_edit.setGeometry(50, 50, 300, 200)

# Set rich text with HTML
text_edit.setHtml("<h1>Welcome</h1><p style='color:blue;'>This is PyQt6 QTextEdit.</p>")

4. Formatting Text

You can format text programmatically using the QTextCursor or setFont(), setAlignment(), etc.

Example: Bold, Italic, and Underlined Text

from PyQt6.QtGui import QTextCursor

text_edit = QTextEdit(window)
text_edit.setGeometry(50, 50, 300, 200)

# Insert formatted text
cursor = text_edit.textCursor()
cursor.insertHtml("<b>Bold Text</b> <i>Italic Text</i> <u>Underlined Text</u>")

Example: Center-Aligned Text

text_edit.setAlignment(Qt.AlignmentFlag.AlignCenter)
text_edit.setText("This text is center-aligned.")

5. Handling Signals for Interactions

The QTextEdit widget provides signals for handling user interactions:

• textChanged: Triggered when the text is modified.
• cursorPositionChanged: Triggered when the cursor position changes.

Example: Handling textChanged

def on_text_changed():
    print("Text has been changed!")

text_edit.textChanged.connect(on_text_changed)

Example: Handling cursorPositionChanged

def on_cursor_position_changed():
    cursor = text_edit.textCursor()
    print(f"Cursor Position: {cursor.position()}")

text_edit.cursorPositionChanged.connect(on_cursor_position_changed)

6. Read-Only QTextEdit

To make QTextEdit read-only, use setReadOnly(True).

Example: Read-Only Mode

text_edit = QTextEdit(window)
text_edit.setGeometry(50, 50, 300, 200)
text_edit.setText("This text cannot be edited.")
text_edit.setReadOnly(True)

7. Styling QTextEdit with CSS

You can customize the appearance of QTextEdit using the setStyleSheet() method.

Example: Custom Style

text_edit.setStyleSheet("""
    QTextEdit {
        background-color: lightyellow;
        color: darkgreen;
        font-size: 16px;
        border: 2px solid darkblue;
        border-radius: 5px;
    }
""")

8. Practical Examples

Example 1: Word Counter

from PyQt6.QtWidgets import QApplication, QMainWindow, QTextEdit, QLabel

def update_word_count():
    text = text_edit.toPlainText()
    word_count = len(text.split())
    label.setText(f"Word Count: {word_count}")

app = QApplication([])
window = QMainWindow()
window.setWindowTitle("Word Counter Example")
window.setGeometry(100, 100, 400, 300)

text_edit = QTextEdit(window)
text_edit.setGeometry(50, 50, 300, 200)
text_edit.textChanged.connect(update_word_count)

label = QLabel("Word Count: 0", window)
label.setGeometry(50, 260, 200, 30)

window.show()
app.exec()

Output:

• Updates the word count dynamically as the user types.

Example 2: Simple Text Editor

from PyQt6.QtWidgets import QApplication, QMainWindow, QTextEdit, QPushButton, QVBoxLayout, QWidget

def save_content():
    with open("output.txt", "w") as file:
        file.write(text_edit.toPlainText())
    print("Content saved to output.txt")

app = QApplication([])
window = QMainWindow()
window.setWindowTitle("Simple Text Editor")
window.setGeometry(100, 100, 500, 400)

central_widget = QWidget(window)
layout = QVBoxLayout(central_widget)

text_edit = QTextEdit()
layout.addWidget(text_edit)

save_button = QPushButton("Save")
save_button.clicked.connect(save_content)
layout.addWidget(save_button)

window.setCentralWidget(central_widget)
window.show()
app.exec()

Output:

• Allows the user to type and save the text content to a file.

Example 3: Highlight Search Term

from PyQt6.QtWidgets import QApplication, QMainWindow, QTextEdit, QLineEdit, QPushButton
from PyQt6.QtGui import QTextCursor

def highlight_text():
    text = search_box.text()
    cursor = text_edit.textCursor()
    cursor.movePosition(QTextCursor.MoveOperation.Start)
    while cursor.find(text):
        cursor.mergeCharFormat(highlight_format)

app = QApplication([])
window = QMainWindow()
window.setWindowTitle("Highlight Search Term")
window.setGeometry(100, 100, 500, 400)

text_edit = QTextEdit(window)
text_edit.setGeometry(50, 50, 400, 200)
text_edit.setText("This is a QTextEdit widget. You can search and highlight text.")

search_box = QLineEdit(window)
search_box.setGeometry(50, 270, 200, 30)
search_box.setPlaceholderText("Enter search term...")

highlight_button = QPushButton("Highlight", window)
highlight_button.setGeometry(270, 270, 100, 30)
highlight_button.clicked.connect(highlight_text)

highlight_format = QTextCursor().charFormat()
highlight_format.setBackground(Qt.GlobalColor.yellow)

window.show()
app.exec()

Output:

• Highlights all occurrences of the search term in the text editor.

Summary

In this tutorial, we covered:

1. Basics of QTextEdit: Creating and configuring the widget.
2. Setting and Retrieving Text: Handling plain and rich text.
3. Formatting: Using rich text and programmatic text formatting.
4. Signals: Handling user interactions like textChanged.
5. Read-Only Mode: Making the widget non-editable.
6. Styling: Customizing appearance with CSS.
7. Practical Examples: Building a word counter, text editor, and search highlighter.

The QTextEdit widget is versatile, making it ideal for applications that require text input or display. Mastering its features allows you to create interactive and visually appealing text-based interfaces in PyQt6.