如何在PyQt文本编辑中使用下标和上标

from PyQt5.QtWidgets import QApplication, QTextEdit
from PyQt5.QtGui import QTextCharFormat, QTextCursor
from PyQt5.QtCore import Qt

app = QApplication([])
text_edit = QTextEdit()

# 设置文本编辑器为富文本模式
text_edit.setAcceptRichText(True)

# 获取当前光标位置
cursor = text_edit.textCursor()

# 插入普通文本
cursor.insertText("H2O")

# 获取当前光标位置
cursor = text_edit.textCursor()

# 设置下标
format_sub = QTextCharFormat()
format_sub.setVerticalAlignment(QTextCharFormat.AlignSubScript)
cursor.setPosition(cursor.position() - 2)  # 设置下标的范围
cursor.setCharFormat(format_sub)
cursor.insertText("2")

# 获取当前光标位置
cursor = text_edit.textCursor()

# 设置上标
format_sup = QTextCharFormat()
format_sup.setVerticalAlignment(QTextCharFormat.AlignSuperScript)
cursor.setPosition(cursor.position() - 1)  # 设置上标的范围
cursor.setCharFormat(format_sup)
cursor.insertText("+")

text_edit.show()
app.exec_()