How can I find a substring and highlight it in QTextEdit?

Question

I have a QTextEdit window that shows the content of a file. I would like to be able to find all matches inside the text using a regex and highlight them either by making th

Answer 1

Here is a sample of how can you highlight text in a QTextEdit:

#!/usr/bin/env python
#-*- coding:utf-8 -*-

from PyQt4.QtGui import *
from PyQt4.QtCore import *

class highlightSyntax(QSyntaxHighlighter):
    def __init__(self, listKeywords, parent=None):
        super(highlightSyntax, self).__init__(parent)
        brush   = QBrush(Qt.darkBlue, Qt.SolidPattern)
        keyword = QTextCharFormat()
        keyword.setForeground(brush)
        keyword.setFontWeight(QFont.Bold)

        self.highlightingRules = [  highlightRule(QRegExp("\\b" + key + "\\b"), keyword)
                                    for key in listKeywords
                                    ]

    def highlightBlock(self, text):
        for rule in self.highlightingRules:
            expression = QRegExp(rule.pattern)
            index      = expression.indexIn(text)

            while index >= 0:
              length = expression.matchedLength()
              self.setFormat(index, length, rule.format)
              index = text.indexOf(expression, index + length)

        self.setCurrentBlockState(0)  

class highlightRule(object):
    def __init__(self, pattern, format):
        self.pattern = pattern
        self.format  = format

class highlightTextEdit(QTextEdit):
    def __init__(self, fileInput, listKeywords, parent=None):
        super(highlightTextEdit, self).__init__(parent)
        highlightSyntax(QStringList(listKeywords), self)

        with open(fileInput, "r") as fInput:
            self.setPlainText(fInput.read())        

if __name__ == "__main__":
    import  sys

    app = QApplication(sys.argv)
    main = highlightTextEdit("/path/to/file", ["foo", "bar", "baz"])
    main.show()
    sys.exit(app.exec_())

Answer 2

I think the simplest solution to your problem is to use the cursor associated to your editor in order to do the formatting. This way you can set the foreground, the background, the font style... The following example marks the matches with a different background.

from PyQt4 import QtGui
from PyQt4 import QtCore

class MyHighlighter(QtGui.QTextEdit):
    def __init__(self, parent=None):
        super(MyHighlighter, self).__init__(parent)
        # Setup the text editor
        text = """In this text I want to highlight this word and only this word.\n""" +\
        """Any other word shouldn't be highlighted"""
        self.setText(text)
        cursor = self.textCursor()
        # Setup the desired format for matches
        format = QtGui.QTextCharFormat()
        format.setBackground(QtGui.QBrush(QtGui.QColor("red")))
        # Setup the regex engine
        pattern = "word"
        regex = QtCore.QRegExp(pattern)
        # Process the displayed document
        pos = 0
        index = regex.indexIn(self.toPlainText(), pos)
        while (index != -1):
            # Select the matched text and apply the desired format
            cursor.setPosition(index)
            cursor.movePosition(QtGui.QTextCursor.EndOfWord, 1)
            cursor.mergeCharFormat(format)
            # Move to the next match
            pos = index + regex.matchedLength()
            index = regex.indexIn(self.toPlainText(), pos)

if __name__ == "__main__":
    import sys
    a = QtGui.QApplication(sys.argv)
    t = MyHighlighter()
    t.show()
    sys.exit(a.exec_())

The code is self-explanatory but if you have any questions just ask them.