qtextedit 显示行号

要在 QTextEdit 中显示行号，您需要将 QTextEdit 放入 QWidget 中，并使用 QVBoxLayout 将 QTextEdit 和 QPlainTextEdit（用于显示行号）垂直地放置在一起。然后，您可以使用 QPlainTextEdit 的 setPlainText() 方法将文本复制到 QPlainTextEdit 中，并使用 QPlainTextEdit 的 lineNumberAreaPaintEvent() 方法绘制行号。

以下是一个简单的示例：

from PyQt5.QtCore import Qt, QRect, QSize
from PyQt5.QtGui import QTextCursor, QPainter, QTextFormat, QColor
from PyQt5.QtWidgets import QWidget, QTextEdit, QVBoxLayout, QPlainTextEdit


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

    def sizeHint(self):
        return QSize(self.editor.lineNumberAreaWidth(), 0)

    def paintEvent(self, event):
        self.editor.lineNumberAreaPaintEvent(event)


class TextEditor(QTextEdit):
    def __init__(self):
        super().__init__()

        self.lineNumberArea = LineNumberArea(self)

        layout = QVBoxLayout()
        layout.addWidget(self.lineNumberArea)
        layout.addWidget(self)

        widget = QWidget()
        widget.setLayout(layout)

        self.setAcceptRichText(False)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setLineWrapMode(QTextEdit.NoWrap)

        self.blockCountChanged.connect(self.updateLineNumberAreaWidth)
        self.updateRequest.connect(self.updateLineNumberArea)
        self.cursorPositionChanged.connect(self.highlightCurrentLine)

        self.updateLineNumberAreaWidth(0)

    def lineNumberAreaWidth(self):
        digits = 1
        count = max(1, self.blockCount())
        while count >= 10:
            count /= 10
            digits += 1
        space = 3 + self.fontMetrics().width('9') * digits
        return space

    def updateLineNumberAreaWidth(self, _):
        self.setViewportMargins(self.lineNumberAreaWidth(), 0, 0, 0)

    def updateLineNumberArea(self, rect, dy):
        if dy:
            self.lineNumberArea.scroll(0, dy)
        else:
            self.lineNumberArea.update(0, rect.y(), self.lineNumberArea.width(),
                                        rect.height())

        if rect.contains(self.viewport().rect()):
            self.updateLineNumberAreaWidth(0)

    def resizeEvent(self, event):
        super().resizeEvent(event)

        cr = self.contentsRect()
        self.lineNumberArea.setGeometry(QRect(cr.left(), cr.top(),
                                                self.lineNumberAreaWidth(), cr.height()))

    def lineNumberAreaPaintEvent(self, event):
        painter = QPainter(self.lineNumberArea)
        painter.fillRect(event.rect(), QColor(240, 240, 240))

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

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

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

    def highlightCurrentLine(self):
        extraSelections = []

        if not self.isReadOnly():
            selection = QTextEdit.ExtraSelection()

            lineColor = QColor(Qt.yellow).lighter(160)

            selection.format.setBackground(lineColor)
            selection.format.setProperty(QTextFormat.FullWidthSelection, True)
            selection.cursor = self.textCursor()
            selection.cursor.clearSelection()
            extraSelections.append(selection)

        self.setExtraSelections(extraSelections)

您可以使用以下代码创建 TextEditor：

text_editor = TextEditor()

然后，您可以将文本添加到 QTextEdit 中，并将其设置为 QPlainTextEdit：

text = 'Hello world!'
text_editor.setPlainText(text)

现在，您可以在行号区域中看到行号，如下所示：