openpyxl 2.4.2: cell value generated by formula empty after saving

Question

I use openpyxl to open a file, edit some cells and save the changes. Here's an example:

  import openpyxl
  book = openpyxl.load_workbook(sheet_path)    
  sheet = book.active

  for row in range(sheet.max_row):
      index = row + 1
      sheet.cell(row=index, column=1).value = "something"

  book.save(sheet_path)

The problem is, when I save the file, other cells are modified. In fact, the cells in my sheet that contains formulas are "corrupted", the file size is greatly reduced and when I use other scripts to read the sheet, the cells containing formulas are reported as empty. But when I open the sheet, everything looks normal and when I save, everything is repaired and the file size is back to normal. I think the problem comes from openpyxl not "calculating" the formulas when saving. This would reduce the file size and require a manual opening/saving in order to get the real cell values. I can't find any way to resolve this issue without completely changing the library I use. Any help would be appreciated, thanks!

Answer 1

When openpyxl reads and writes existing formulas, the computed values are omitted, and no values are computed for new formulas. openpyxl sets a flag in the workbook that tells excel to recompute formula values on load, which is why everything looks normal when you look at it with excel.