Losing merged cells border while editing Excel file with openpyxl

Question

I have two sheets in an Excel file and the first one is a cover sheet which I don't need to edit. There are a few merged cells in the cover sheet, and when I edit the file using openpyxl, without even touching the cover sheet, I lose borders from the merged cells. I am using load_workbook('excel file') to load the Excel file and saving it with a different filename.

Is there any way to fix this problem?

Answer 1

Actual solution is to patch the libraries code by including this snippet after including the library, it fixes the problem. (Note: don't worry about missing definitions, e.g. COORD_RE, i.e. the patch is self-contained)

from itertools import product
import types
import openpyxl
from openpyxl import worksheet
from openpyxl.utils import range_boundaries


def patch_worksheet():
    """This monkeypatches Worksheet.merge_cells to remove cell deletion bug
    https://bitbucket.org/openpyxl/openpyxl/issues/365/styling-merged-cells-isnt-working
    Thank you to Sergey Pikhovkin for the fix
    """

    def merge_cells(self, range_string=None, start_row=None, start_column=None, end_row=None, end_column=None):
        """ Set merge on a cell range.  Range is a cell range (e.g. A1:E1)
        This is monkeypatched to remove cell deletion bug
        https://bitbucket.org/openpyxl/openpyxl/issues/365/styling-merged-cells-isnt-working
        """
        if not range_string and not all((start_row, start_column, end_row, end_column)):
            msg = "You have to provide a value either for 'coordinate' or for\
            'start_row', 'start_column', 'end_row' *and* 'end_column'"
            raise ValueError(msg)
        elif not range_string:
            range_string = '%s%s:%s%s' % (get_column_letter(start_column),
                                          start_row,
                                          get_column_letter(end_column),
                                          end_row)
        elif ":" not in range_string:
            if COORD_RE.match(range_string):
                return  # Single cell, do nothing
            raise ValueError("Range must be a cell range (e.g. A1:E1)")
        else:
            range_string = range_string.replace('$', '')

        if range_string not in self._merged_cells:
            self._merged_cells.append(range_string)


        # The following is removed by this monkeypatch:

        # min_col, min_row, max_col, max_row = range_boundaries(range_string)
        # rows = range(min_row, max_row+1)
        # cols = range(min_col, max_col+1)
        # cells = product(rows, cols)

        # all but the top-left cell are removed
        #for c in islice(cells, 1, None):
            #if c in self._cells:
                #del self._cells[c]

    # Apply monkey patch
    worksheet.Worksheet.merge_cells = merge_cells
patch_worksheet()

Source https://bitbucket.org/openpyxl/openpyxl/issues/365/styling-merged-cells-isnt-working

Answer 2

I know this is old but I got the same issue and the patch didn't work for me so I found a work around by using the function in the documentation that adds a style for merged cells and then looping on all the merged cells and calling the function on each range

from openpyxl import load_workbook
from openpyxl.styles import Border, Side, PatternFill, Font, GradientFill, 
Alignment

def style_range(ws, cell_range, border=Border(), fill=None, font=None, 
alignment=None):
    """
    Apply styles to a range of cells as if they were a single cell.

    :param ws:  Excel worksheet instance
    :param range: An excel range to style (e.g. A1:F20)
    :param border: An openpyxl Border
    :param fill: An openpyxl PatternFill or GradientFill
    :param font: An openpyxl Font object
    """

    top = Border(top=border.top)
    left = Border(left=border.left)
    right = Border(right=border.right)
    bottom = Border(bottom=border.bottom)

    first_cell = ws[cell_range.split(":")[0]]
    if alignment:
        ws.merge_cells(cell_range)
        first_cell.alignment = alignment

    rows = ws[cell_range]
    if font:
        first_cell.font = font

    for cell in rows[0]:
        cell.border = cell.border + top
    for cell in rows[-1]:
        cell.border = cell.border + bottom

    for row in rows:
        l = row[0]
        r = row[-1]
        l.border = l.border + left
        r.border = r.border + right
        if fill:
            for c in row:
                c.fill = fill

file = 'file.xlsx'

wb = load_workbook(file)
ws = wb['Table 1']

thin = Side(border_style="thin", color="000000")
border = Border(top=thin, left=thin, right=thin, bottom=thin)

for range in ws.merged_cells.ranges:
    style_range(ws, str(range), border=border)

wb.save('newExcel.xlsx')