I need to read the range of merge cells in an excel file. The file size is about 4GB.

I have tried openpyxl package.

When I load_workbook in normal mode, I can get the range with sheet.merged_cells.ranges.

But the loading is very slow and take too much memories.

When I using read_only mode, the loading is fast but there is an Attribute error AttributeError: ‘ReadOnlyWorksheet’ object has no attribute ‘merged_cells’.

Is there any other package (not limited to python packages) can read merged ranges with limited memory?