PyQt6: Working with QPlainTextEdit for Plain Text

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PyQt6: Working with QPlainTextEdit for Plain Text

Plain text editing is a fundamental feature in many GUI applications, from simple note-taking apps to complex code editors. In PyQt6, the QPlainTextEdit widget provides a powerful and efficient way to handle plain text editing. Unlike QTextEdit, which supports rich text, QPlainTextEdit is optimized for plain text and is particularly suitable for handling large text files.

In this article, we will explore the various features of QPlainTextEdit and demonstrate how to use them to create a plain text editor. We will start by setting up our development environment and creating a simple QPlainTextEdit widget. From there, we will delve into basic text operations, text formatting options, and handling signals.

We will also cover advanced features such as implementing line numbers and syntax highlighting, as well as integrating QPlainTextEdit with other widgets to create a comprehensive text editor interface.

By the end of this article, you will have a solid understanding of how to use QPlainTextEdit in your PyQt6 applications and be ready to build your own plain text editors.

Setting Up the Development Environment

Before we dive into creating and customizing QPlainTextEdit, we need to set up our development environment. This includes installing Python and PyQt6, and ensuring we have everything ready to start writing and running PyQt6 applications.

Installing Python and PyQt6

To get started, ensure you have Python installed on your computer. PyQt6 requires Python 3.6 or later. You can download the latest version of Python from the official Python website. Once Python is installed, open your command prompt or terminal and install PyQt6 using the pip package manager by running the following command:

pip install PyQt6

This command will download and install PyQt6 along with all its dependencies.

Setting Up a Development Environment

To write and run your PyQt6 code, you can use any text editor or Integrated Development Environment (IDE). Some popular choices include PyCharm, a powerful IDE for Python with support for PyQt6; VS Code, a lightweight and versatile code editor with Python extensions; and Sublime Text, a simple yet efficient text editor. Choose the one that you’re most comfortable with.

Writing a Simple PyQt6 Application

To ensure everything is set up correctly, let’s write a simple PyQt6 application that creates a window with a QPlainTextEdit widget.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named simple_qplaintextedit.py.
  2. Write the Code: Copy and paste the following code into your simple_qplaintextedit.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QVBoxLayout

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('QPlainTextEdit Example')
window.setGeometry(100, 100, 600, 400)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Enter your text here...')

# Add the QPlainTextEdit to the layout
layout.addWidget(plain_text_edit)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window appear with a QPlainTextEdit widget displaying the placeholder text “Enter your text here…”.

In the code above, we start by importing the necessary modules from PyQt6, including QApplication, QWidget, QPlainTextEdit, and QVBoxLayout.

Next, we create an instance of the QApplication class, which is required for any PyQt6 application. This instance manages application-wide resources and settings.

We then create an instance of QWidget, which serves as the main window of the application. We set the title of the window using the setWindowTitle method and define the position and size of the window using the setGeometry method.

A QPlainTextEdit widget is created and added to the main window. The setPlaceholderText method is used to set placeholder text for the QPlainTextEdit widget, which helps guide users on what to input.

To arrange the QPlainTextEdit widget vertically within the window, we create a QVBoxLayout instance. The addWidget method is then used to add the QPlainTextEdit to the layout. We set this layout for the main window using the setLayout method.

Finally, we display the main window using the show method and start the application’s event loop with sys.exit(app.exec()). This event loop waits for user interactions and handles them accordingly, keeping the application running until the user closes the window.

By following these steps, you have successfully set up your development environment and created a simple PyQt6 application with a QPlainTextEdit widget. In the next sections, we’ll explore how to customize and enhance QPlainTextEdit with various features and functionalities.

Creating a Basic QPlainTextEdit

The QPlainTextEdit widget is designed for plain text editing, providing a lightweight and efficient way to handle large text files. In this section, we will explore the basics of creating and using a QPlainTextEdit widget in a PyQt6 application.

Introduction to QPlainTextEdit

QPlainTextEdit is a multi-line text editor widget that supports plain text. It is optimized for handling large text files and provides various methods for manipulating text, such as adding, modifying, and clearing text. Unlike QTextEdit, which supports rich text and HTML, QPlainTextEdit focuses solely on plain text, making it more efficient for certain use cases.

Code Example: Creating a Basic QPlainTextEdit

To create a basic QPlainTextEdit, follow these steps:

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named basic_qplaintextedit.py.
  2. Write the Code: Copy and paste the following code into your basic_qplaintextedit.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QVBoxLayout

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Basic QPlainTextEdit Example')
window.setGeometry(100, 100, 600, 400)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Enter your text here...')

# Add the QPlainTextEdit to the layout
layout.addWidget(plain_text_edit)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window appear with a QPlainTextEdit widget displaying the placeholder text “Enter your text here…”.

By following these steps, you have created a basic QPlainTextEdit widget in a PyQt6 application. In the next sections, we will explore various text operations, formatting options, and handling signals in QPlainTextEdit.

Basic Text Operations

QPlainTextEdit provides a range of methods for basic text operations, including adding, modifying, and clearing text. It also supports setting placeholder text to guide users. In this section, we will explore these basic text operations with code examples.

Adding, Modifying, and Clearing Text

You can easily add, modify, and clear text in a QPlainTextEdit widget using methods like setPlainText, appendPlainText, and clear.

  1. Adding Text: Use the setPlainText method to set the text of the QPlainTextEdit widget.
plain_text_edit.setPlainText('This is a sample text.')

  1. Modifying Text: Use the appendPlainText method to add text to the existing content.
plain_text_edit.appendPlainText('Appending more text.')

  1. Clearing Text: Use the clear method to clear all the text in the QPlainTextEdit widget.
plain_text_edit.clear()

Setting Placeholder Text

Placeholder text is useful for guiding users on what to input in the QPlainTextEdit widget. Use the setPlaceholderText method to set placeholder text.

plain_text_edit.setPlaceholderText('Enter your text here...')

Code Example: Basic Text Operations

Let’s create a PyQt6 application that demonstrates basic text operations in a QPlainTextEdit widget.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named text_operations.py.
  2. Write the Code: Copy and paste the following code into your text_operations.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QPushButton, QVBoxLayout, QHBoxLayout

# Slot function to add text
def add_text():
    plain_text_edit.setPlainText('This is a sample text.')

# Slot function to modify text
def modify_text():
    plain_text_edit.appendPlainText('Appending more text.')

# Slot function to clear text
def clear_text():
    plain_text_edit.clear()

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Text Operations Example')
window.setGeometry(100, 100, 600, 400)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Enter your text here...')

# Create buttons for text operations
add_button = QPushButton('Add Text')
modify_button = QPushButton('Modify Text')
clear_button = QPushButton('Clear Text')

# Connect buttons to their slot functions
add_button.clicked.connect(add_text)
modify_button.clicked.connect(modify_text)
clear_button.clicked.connect(clear_text)

# Create a horizontal layout for the buttons
button_layout = QHBoxLayout()
button_layout.addWidget(add_button)
button_layout.addWidget(modify_button)
button_layout.addWidget(clear_button)

# Add the button layout and QPlainTextEdit to the main layout
layout.addLayout(button_layout)
layout.addWidget(plain_text_edit)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit widget and three buttons labeled “Add Text,” “Modify Text,” and “Clear Text.” You can click the buttons to add, modify, and clear text in the QPlainTextEdit.

By following these steps, you have demonstrated basic text operations in a QPlainTextEdit widget. In the next sections, we will explore text formatting options and handling signals in QPlainTextEdit.

Text Formatting Options

While QPlainTextEdit is primarily designed for plain text, you can still apply basic text formatting such as changing the font, font size, and text color. These options allow you to customize the appearance of the text within the widget, making it more readable and visually appealing.

Applying Basic Formatting

You can set the font, font size, and text color for the entire text in QPlainTextEdit using the setFont, setFontPointSize, and setTextColor methods. Note that these settings apply to all the text within the QPlainTextEdit.

Code Example: Applying Text Formatting

Let’s create a PyQt6 application that allows users to apply basic text formatting to the content of a QPlainTextEdit widget.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named text_formatting.py.
  2. Write the Code: Copy and paste the following code into your text_formatting.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QPushButton, QVBoxLayout, QHBoxLayout, QFontDialog, QColorDialog

# Slot function to set font
def set_font():
    font, ok = QFontDialog.getFont()
    if ok:
        plain_text_edit.setFont(font)

# Slot function to set text color
def set_text_color():
    color = QColorDialog.getColor()
    if color.isValid():
        plain_text_edit.setStyleSheet(f"color: {color.name()};")

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Text Formatting Example')
window.setGeometry(100, 100, 600, 400)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Enter your text here...')

# Create buttons for text formatting
font_button = QPushButton('Set Font')
color_button = QPushButton('Set Text Color')

# Connect buttons to their slot functions
font_button.clicked.connect(set_font)
color_button.clicked.connect(set_text_color)

# Create a horizontal layout for the buttons
button_layout = QHBoxLayout()
button_layout.addWidget(font_button)
button_layout.addWidget(color_button)

# Add the button layout and QPlainTextEdit to the main layout
layout.addLayout(button_layout)
layout.addWidget(plain_text_edit)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit widget and two buttons labeled “Set Font” and “Set Text Color.” You can use these buttons to change the font and text color of the content in the QPlainTextEdit.

By following these steps, you have demonstrated how to apply basic text formatting in a QPlainTextEdit widget. In the next section, we will explore handling signals in QPlainTextEdit.

Handling QPlainTextEdit Signals

QPlainTextEdit emits various signals that can be connected to custom slot functions to handle user interactions. These signals allow you to respond to changes in the text, cursor movements, and other events in real-time, making your application more interactive and responsive. In this section, we’ll explore some of the commonly used signals in QPlainTextEdit and demonstrate how to connect them to slot functions.

Introduction to QPlainTextEdit Signals

Signals are emitted by QPlainTextEdit when specific events occur. Some of the most commonly used signals include:

  • textChanged: Emitted whenever the text in the QPlainTextEdit changes.
  • cursorPositionChanged: Emitted whenever the cursor position changes.

By connecting these signals to custom slot functions, you can define how your application should respond to these events.

Code Example: Handling textChanged and cursorPositionChanged Signals

Let’s create a PyQt6 application that connects to the textChanged and cursorPositionChanged signals of QPlainTextEdit to update a QLabel with the current status of the text and cursor position.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named textedit_signals.py.
  2. Write the Code: Copy and paste the following code into your textedit_signals.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QLabel, QVBoxLayout

# Slot function to update text status
def update_text_status():
    status_label.setText(f'Text length: {len(plain_text_edit.toPlainText())} characters')

# Slot function to update cursor position
def update_cursor_position():
    cursor = plain_text_edit.textCursor()
    status_label.setText(f'Cursor position: {cursor.position()}')

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('QPlainTextEdit Signals Example')
window.setGeometry(100, 100, 600, 400)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Enter your text here...')

# Create a QLabel instance to display status
status_label = QLabel('Text length: 0 characters', window)

# Connect the signals to their slot functions
plain_text_edit.textChanged.connect(update_text_status)
plain_text_edit.cursorPositionChanged.connect(update_cursor_position)

# Add the QPlainTextEdit and QLabel to the layout
layout.addWidget(plain_text_edit)
layout.addWidget(status_label)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit widget and a QLabel displaying the text length. As you type in the QPlainTextEdit, the QLabel will update to show the current text length. When you move the cursor, the QLabel will update to show the cursor’s current position.

By following these steps, you have created a PyQt6 application that handles various signals emitted by QPlainTextEdit, making your application more interactive and responsive to user actions. In the next sections, we will explore how to use QPlainTextEdit for large text files and implement advanced features such as line numbers and syntax highlighting.

Using QPlainTextEdit for Large Text Files

One of the significant advantages of QPlainTextEdit over QTextEdit is its efficiency in handling large text files. QPlainTextEdit is optimized for plain text and can handle large volumes of text more smoothly. In this section, we will explore how to load and display large text files efficiently using QPlainTextEdit.

Advantages of QPlainTextEdit for Large Text Files

QPlainTextEdit is designed to manage plain text with better performance, especially when dealing with large text files. It provides a more responsive experience for users, making it suitable for applications like log viewers, code editors, and text processors.

Code Example: Loading and Displaying Large Text Files

Let’s create a PyQt6 application that loads and displays a large text file in a QPlainTextEdit widget.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named large_text_file.py.
  2. Write the Code: Copy and paste the following code into your large_text_file.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QPushButton, QVBoxLayout, QFileDialog


# Slot function to load a large text file
def load_text_file():
    options = QFileDialog.options(QFileDialog())
    file_path, _ = QFileDialog.getOpenFileName(window, "Open Text File", "", "Text Files (*.txt);;All Files (*)",
                                               options=options)
    if file_path:
        with open(file_path, 'r', encoding='utf-8') as file:
            plain_text_edit.setPlainText(file.read())


# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Load Large Text File Example')
window.setGeometry(100, 100, 800, 600)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Load a text file to display its contents here...')

# Create a QPushButton for loading a text file
load_button = QPushButton('Load Text File')

# Connect the button to the slot function
load_button.clicked.connect(load_text_file)

# Add the button and QPlainTextEdit to the main layout
layout.addWidget(load_button)
layout.addWidget(plain_text_edit)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit widget and a button labeled “Load Text File.” When you click the button, a file dialog will open, allowing you to select a text file to load. The contents of the selected file will be displayed in the QPlainTextEdit.

By following these steps, you have created a PyQt6 application that efficiently loads and displays large text files in a QPlainTextEdit widget. In the next sections, we will explore how to implement advanced features such as line numbers and syntax highlighting.

Advanced Features

QPlainTextEdit offers various advanced features that can enhance its functionality and user experience. In this section, we will explore how to implement line numbers and syntax highlighting, which are particularly useful for applications like code editors and log viewers.

Implementing Line Numbers

Adding line numbers to a QPlainTextEdit can help users navigate and reference text more easily. This feature is commonly found in code editors and text editors.

Code Example: Adding Line Numbers

Let’s create a PyQt6 application that adds line numbers to a QPlainTextEdit widget.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named line_numbers.py.
  2. Write the Code: Copy and paste the following code into your line_numbers.py file:
import sys
from PyQt6.QtCore import Qt, QRect, QSize
from PyQt6.QtGui import QPainter, QColor, QTextFormat
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QVBoxLayout, QTextEdit


class LineNumberArea(QWidget):
    def __init__(self, editor):
        super().__init__(editor)
        self.code_editor = editor

    def sizeHint(self):
        return QSize(self.code_editor.line_number_area_width(), 0)

    def paintEvent(self, event):
        self.code_editor.line_number_area_paint_event(event)


class CodeEditor(QPlainTextEdit):
    def __init__(self):
        super().__init__()
        self.line_number_area = LineNumberArea(self)

        # Connect signals
        self.blockCountChanged.connect(self.update_line_number_area_width)
        self.updateRequest.connect(self.update_line_number_area)
        self.cursorPositionChanged.connect(self.highlight_current_line)

        self.update_line_number_area_width(0)

    def line_number_area_width(self):
        digits = len(str(self.blockCount()))
        space = 3 + self.fontMetrics().horizontalAdvance('9') * digits
        return space

    def update_line_number_area_width(self, _):
        self.setViewportMargins(self.line_number_area_width(), 0, 0, 0)

    def update_line_number_area(self, rect, dy):
        # Ensure that updateRequest is handled safely
        if dy != 0:
            self.line_number_area.scroll(0, dy)
        else:
            self.line_number_area.update(0, rect.y(), self.line_number_area.width(), rect.height())

        # Ensure the area updates correctly if required
        if rect.contains(self.viewport().rect()):
            self.update_line_number_area_width(0)

    def resizeEvent(self, event):
        super().resizeEvent(event)
        cr = self.contentsRect()
        self.line_number_area.setGeometry(QRect(cr.left(), cr.top(), self.line_number_area_width(), cr.height()))

    def line_number_area_paint_event(self, event):
        painter = QPainter(self.line_number_area)
        painter.fillRect(event.rect(), Qt.GlobalColor.lightGray)

        block = self.firstVisibleBlock()
        block_number = block.blockNumber()
        top = self.blockBoundingGeometry(block).translated(self.contentOffset()).top()
        bottom = top + self.blockBoundingRect(block).height()

        while block.isValid() and top <= event.rect().bottom():
            if block.isVisible() and bottom >= event.rect().top():
                number = str(block_number + 1)
                painter.setPen(Qt.GlobalColor.black)
                painter.drawText(0, int(top), self.line_number_area.width(), self.fontMetrics().height(),
                                 Qt.AlignmentFlag.AlignRight, number)

            block = block.next()
            top = bottom
            bottom = top + self.blockBoundingRect(block).height()
            block_number += 1

    def highlight_current_line(self):
        extra_selections = []

        if not self.isReadOnly():
            selection = QTextEdit.ExtraSelection()
            line_color = QColor(Qt.GlobalColor.yellow).lighter(160)
            selection.format.setBackground(line_color)
            selection.cursor = self.textCursor()
            selection.cursor.clearSelection()
            extra_selections.append(selection)

        self.setExtraSelections(extra_selections)


app = QApplication(sys.argv)

# Create an instance of CodeEditor
editor = CodeEditor()
editor.setPlaceholderText('Enter your code here...')

# Set up the layout and window
window = QWidget()
layout = QVBoxLayout()
layout.addWidget(editor)
window.setLayout(layout)

window.setWindowTitle('Code Editor with Line Numbers')
window.setGeometry(100, 100, 800, 600)

# Show the window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit widget that displays line numbers next to the text. The current line is highlighted, and the line numbers update as you scroll or add new lines.

In this example, we create a custom widget LineNumberArea that displays line numbers next to the text in a QPlainTextEdit. We then create a CodeEditor class that extends QPlainTextEdit and integrates the LineNumberArea.

  • The LineNumberArea class overrides the paintEvent method to draw line numbers.
  • The CodeEditor class:
  • Initializes the LineNumberArea.
  • Connects various signals to update the line number area when necessary.
  • Overrides the resizeEvent to adjust the LineNumberArea geometry.
  • Implements methods to calculate the width of the line number area and draw the line numbers.
  • Highlights the current line using highlight_current_line.

By following these steps, you have added line numbers to a QPlainTextEdit widget. In the next section, we will explore how to implement syntax highlighting.

Implementing Syntax Highlighting

Syntax highlighting is a feature commonly found in code editors that highlights keywords, comments, and other elements of the code in different colors. This makes the code easier to read and understand.

Code Example: Adding Syntax Highlighting

Let’s create a PyQt6 application that adds basic syntax highlighting to a QPlainTextEdit widget.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named syntax_highlighting.py.
  2. Write the Code: Copy and paste the following code into your syntax_highlighting.py file:
import sys
import re
from PyQt6.QtCore import Qt
from PyQt6.QtGui import QSyntaxHighlighter, QTextCharFormat, QFont, QColor
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QVBoxLayout


class SyntaxHighlighter(QSyntaxHighlighter):
    def __init__(self, parent=None):
        super().__init__(parent)
        self._highlighting_rules = []

        # Keywords
        keyword_format = QTextCharFormat()
        keyword_format.setForeground(Qt.GlobalColor.blue)
        keyword_format.setFontWeight(QFont.Weight.Bold)
        keywords = [
            '\\bclass\\b', '\\bdef\\b', '\\breturn\\b', '\\bif\\b', '\\belse\\b', '\\bimport\\b'
        ]
        for keyword in keywords:
            self._highlighting_rules.append((re.compile(keyword), keyword_format))

        # Strings
        string_format = QTextCharFormat()
        string_format.setForeground(Qt.GlobalColor.darkGreen)
        self._highlighting_rules.append((re.compile('".*?"'), string_format))
        self._highlighting_rules.append((re.compile("'.*?'"), string_format))

        # Comments
        comment_format = QTextCharFormat()
        comment_format.setForeground(Qt.GlobalColor.darkGray)
        self._highlighting_rules.append((re.compile('#[^\n]*'), comment_format))

    def highlightBlock(self, text):
        for pattern, format in self._highlighting_rules:
            for match in pattern.finditer(text):
                start, end = match.span()
                self.setFormat(start, end - start, format)


# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit()
plain_text_edit.setPlaceholderText('Enter your code here...')

# Apply syntax highlighting
highlighter = SyntaxHighlighter(plain_text_edit.document())

# Create a QVBoxLayout instance
layout = QVBoxLayout()
layout.addWidget(plain_text_edit)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Syntax Highlighting Example')
window.setGeometry(100, 100, 800, 600)
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit widget that highlights Python keywords, strings, and comments in different colors.

In this example, we create a custom SyntaxHighlighter class that extends QSyntaxHighlighter to apply syntax highlighting rules.

  • The SyntaxHighlighter class defines highlighting rules for Python keywords, strings, and comments using regular expressions.
  • The highlightBlock method applies the highlighting rules to each block of text.

By following these steps, you have added basic syntax highlighting to a QPlainTextEdit widget. In the next sections, we will explore integrating QPlainTextEdit with other widgets and styling it with Qt Style Sheets.

Integrating QPlainTextEdit with Other Widgets

Integrating QPlainTextEdit with other widgets is essential for creating comprehensive and interactive user interfaces in your PyQt6 applications. By combining QPlainTextEdit with layout managers and other PyQt6 widgets, you can build complex and responsive interfaces. This section will guide you through the process of integrating QPlainTextEdit with other widgets and demonstrate how to create a user-friendly form layout.

Combining QPlainTextEdit with Other Widgets in Layouts

To create well-organized interfaces, you need to use layout managers like QVBoxLayout, QHBoxLayout, and QFormLayout. These layout managers help you arrange widgets systematically within the main window. In this example, we’ll use a form layout to integrate QPlainTextEdit with other widgets such as QLabel and QPushButton.

Code Example: Using QPlainTextEdit in a Form Layout

Let’s create a simple form with labels, line edits for user input, a QPlainTextEdit for detailed input, and a submit button.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named form_layout.py.
  2. Write the Code: Copy and paste the following code into your form_layout.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QLabel, QLineEdit, QPlainTextEdit, QPushButton, QVBoxLayout, QFormLayout

# Slot function to handle button click
def on_submit():
    name = name_input.text()
    email = email_input.text()
    bio = bio_input.toPlainText()
    print(f'Name: {name}, Email: {email}, Bio: {bio}')

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Form Layout Example')
window.setGeometry(100, 100, 600, 400)

# Create a QFormLayout instance
form_layout = QFormLayout()

# Create QLabel and QLineEdit instances for name
name_label = QLabel('Name:')
name_input = QLineEdit()

# Create QLabel and QLineEdit instances for email
email_label = QLabel('Email:')
email_input = QLineEdit()

# Create QLabel and QPlainTextEdit instances for bio
bio_label = QLabel('Bio:')
bio_input = QPlainTextEdit()
bio_input.setPlaceholderText('Tell us about yourself...')

# Add widgets to the form layout
form_layout.addRow(name_label, name_input)
form_layout.addRow(email_label, email_input)
form_layout.addRow(bio_label, bio_input)

# Create a QPushButton for submitting the form
submit_button = QPushButton('Submit')
submit_button.clicked.connect(on_submit)

# Create a QVBoxLayout to combine the form layout and submit button
main_layout = QVBoxLayout()
main_layout.addLayout(form_layout)
main_layout.addWidget(submit_button)

# Set the layout for the main window
window.setLayout(main_layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a form containing labels, text input fields, a QPlainTextEdit for detailed input, and a submit button. When you enter text in the fields and click the submit button, the input values are printed in the console.

By integrating multiple widgets and layout managers, you can create more complex and interactive user interfaces. For instance, you can add additional buttons, input fields, and other widgets to enhance the functionality of your form.

Styling QPlainTextEdit with Qt Style Sheets

Styling your QPlainTextEdit widgets can significantly enhance the visual appeal and usability of your PyQt6 applications. Qt Style Sheets (QSS) allow you to customize the appearance of QPlainTextEdit, enabling you to change its background color, border, font, and more. In this section, we’ll explore how to apply styles to QPlainTextEdit using Qt Style Sheets.

Introduction to Styling with QSS

Qt Style Sheets provide a way to apply CSS-like styling to Qt widgets. This allows you to define the look and feel of your application in a flexible and maintainable manner. With QSS, you can control various aspects of QPlainTextEdit’s appearance, including colors, fonts, borders, and padding.

Applying Styles to QPlainTextEdit

You can apply styles to a QPlainTextEdit by using the setStyleSheet method. This method takes a string containing the style rules and applies them to the widget.

Code Example: Customizing QPlainTextEdit Appearance with Styles

Let’s create a PyQt6 application with a QPlainTextEdit that has customized styles.

  1. Create a New Python File: Open your IDE or text editor and create a new Python file named styled_qplaintextedit.py.
  2. Write the Code: Copy and paste the following code into your styled_qplaintextedit.py file:
import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPlainTextEdit, QVBoxLayout

# Create an instance of QApplication
app = QApplication(sys.argv)

# Create a QWidget instance (main window)
window = QWidget()
window.setWindowTitle('Styled QPlainTextEdit Example')
window.setGeometry(100, 100, 600, 400)

# Create a QVBoxLayout instance
layout = QVBoxLayout()

# Create a QPlainTextEdit instance
plain_text_edit = QPlainTextEdit(window)
plain_text_edit.setPlaceholderText('Enter your text here...')

# Apply styles to the QPlainTextEdit
plain_text_edit.setStyleSheet("""
    QPlainTextEdit {
        background-color: #f0f0f0;  /* Light gray background */
        color: #007ACC;  /* Blue text color */
        border: 2px solid #007ACC;  /* Blue border */
        border-radius: 5px;  /* Rounded corners */
        font-size: 16px;  /* Font size */
        padding: 5px;  /* Padding */
    }
    QPlainTextEdit:hover {
        background-color: #e0e0e0;  /* Darker gray on hover */
    }
    QPlainTextEdit:focus {
        border: 2px solid #FF6347;  /* Red border when focused */
    }
""")

# Add the QPlainTextEdit to the layout
layout.addWidget(plain_text_edit)

# Set the layout for the main window
window.setLayout(layout)

# Show the main window
window.show()

# Run the application's event loop
sys.exit(app.exec())

  1. Run the Script: Save your file and run it. You should see a window with a QPlainTextEdit that has a light gray background, blue text, a blue border with rounded corners, and additional padding. The background color changes to a darker gray when hovered over, and the border color changes to red when the QPlainTextEdit is focused.

In the code above, we start by importing the necessary modules from PyQt6, including QApplication, QWidget, QPlainTextEdit, and QVBoxLayout.

We then create an instance of QApplication and a main window using QWidget. The window title and size are set using setWindowTitle and setGeometry.

A QPlainTextEdit widget is created and added to the main window with a placeholder text using the setPlaceholderText method. We apply custom styles to the QPlainTextEdit using the setStyleSheet method.

  • Background Color: The background-color property sets the background color of the QPlainTextEdit to light gray.
background-color: #f0f0f0;

  • Text Color: The color property sets the text color to blue.
color: #007ACC;

  • Border: The border property defines a 2-pixel solid blue border around the QPlainTextEdit.
border: 2px solid #007ACC;

  • Border Radius: The border-radius property rounds the corners of the QPlainTextEdit with a radius of 5 pixels.
border-radius: 5px;

  • Font Size: The font-size property sets the font size to 16 pixels.
font-size: 16px;

  • Padding: The padding property adds 5 pixels of padding inside the QPlainTextEdit, providing space between the text and the border.
padding: 5px;

  • Hover State: The :hover pseudo-class changes the background color to a darker gray when the QPlainTextEdit is hovered over.
QPlainTextEdit:hover {
  background-color: #e0e0e0;
}

  • Focus State: The :focus pseudo-class changes the border color to red when the QPlainTextEdit is focused.
QPlainTextEdit:focus {
  border: 2px solid #FF6347;
}

By using Qt Style Sheets, you can create visually appealing QPlainTextEdit widgets that enhance the user interface of your PyQt6 applications. Experiment with different styles and properties to achieve the desired look and feel for your application.

Conclusion

In this article, we explored the versatile and powerful QPlainTextEdit widget in PyQt6. We started with an introduction to QPlainTextEdit and its importance in GUI applications. We then walked through setting up your development environment, creating a basic QPlainTextEdit, and customizing it with placeholder text, text alignment, and maximum input length.

We demonstrated how to handle QPlainTextEdit signals, such as textChanged and cursorPositionChanged, to make your application more interactive. We also explored how to style QPlainTextEdit with Qt Style Sheets, making it visually appealing and user-friendly.

We then integrated QPlainTextEdit with other widgets to create complex layouts, showcasing how to build a user-friendly form.

The examples and concepts covered in this article provide a solid foundation for working with QPlainTextEdit in PyQt6. However, the possibilities are endless. I encourage you to experiment further and explore more advanced features and customizations. Try combining QPlainTextEdit with other PyQt6 widgets and see how you can create rich, interactive user interfaces. Don’t hesitate to experiment with different styles, signals, and slots to make your applications unique and engaging.

Additional Resources for Learning PyQt6 and QPlainTextEdit

To continue your journey with PyQt6 and QPlainTextEdit, here are some additional resources that will help you expand your knowledge and skills:

  1. PyQt6 Documentation: The official documentation is a comprehensive resource for understanding the capabilities and usage of PyQt6. PyQt6 Documentation
  2. Online Tutorials and Courses: Websites like Real Python, Udemy, and Coursera offer detailed tutorials and courses on PyQt6, catering to different levels of expertise.
  3. Books: Books such as “Rapid GUI Programming with Python and Qt” by Mark Summerfield provide in-depth insights and practical examples.
  4. Community and Forums: Join online communities and forums like Stack Overflow, Reddit, and the PyQt mailing list to connect with other PyQt developers, ask questions, and share knowledge.
  5. Sample Projects and Open Source: Explore sample projects and open-source PyQt6 applications on GitHub to see how others have implemented various features and functionalities.

By leveraging these resources and continuously practicing, you’ll become proficient in PyQt6 and be well on your way to developing impressive and functional desktop applications.

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