我自己想出来的。您可以在保存工作簿时捕获XML，而不是通过解压缩保存的工作簿来提取XML。wb.save方法使用了ExcelWriter类，我修改了这个类以适应这个目的：

import openpyxl
from openpyxl.writer.excel import *

class MyExcelWriter(openpyxl.writer.excel.ExcelWriter):
    def write_worksheet(self, ws):
        ws._drawing = SpreadsheetDrawing()
        ws._drawing.charts = ws._charts
        ws._drawing.images = ws._images
        if self.workbook.write_only:
            if not ws.closed:
                ws.close()
            writer = ws._writer
        else:
            writer = WorksheetWriter(ws)
            writer.write()
        ws._rels = writer._rels
        
        # my addition starts here
        if ws.title == 'My Sheet':
            with open(writer.out, 'r', encoding='utf8') as file:
                xml_code = file.read()

            # my code continues here...
        # my addition ends here

        self._archive.write(writer.out, ws.path[1:])
        self.manifest.append(ws)
        writer.cleanup()

openpyxl.writer.excel.ExcelWriter = MyExcelWriter

write_worksheet函数创建一个临时xml文件，其路径存储在writer.out中。
记住from <module> import *is considered bad practice-谨慎使用。