PyQt5 QRegExp问题

Question

怎么回事，查找只匹配第一个空格前的部分，我希望不用正则全部匹配？

def btnfind_fun(self):
    pattern = self.codeline.text()
    if len(pattern)>0 and pattern!=' ' :
        cursor = self.CodetextEdit.textCursor()
        # Setup the desired format for matches
        format = QtGui.QTextCharFormat()
        format.setBackground(QtGui.QBrush(QtGui.QColor("red")))
        # Setup the regex engine
        regex = QRegExp(pattern,QtCore.Qt.CaseInsensitive)
        # Process the displayed document
        pos = 0
        index = regex.indexIn(self.CodetextEdit.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.CodetextEdit.toPlainText(), pos)
        self.CodetextEdit.moveCursor(pos)![image.png](/img/bVbRYyx)

另外，如何在着色前清除上次的着色