Apply format to a cell after being written in XlsxWriter

Question

I work on python using XlsxWriter and I've been trying to solve this problem with no success:

My app must create an Xlsx file in which data is shown in a table-like structure. That table has some empty cells.

I'd like to set borders to some cells to make a grid for the table so I use:

format6 = excelbook.add_format()
format6.set_left(1)
for y in range(24):
    excel.write(y+5, 1, None, format6)

in order to have border applied to those cells. Then, I write data on the table.

Since the table layout is quite complex, it would be easy to write data and, once everything is written, apply format to cells to have borders, but I can't find the way.

Is there any way to apply format to a cell once it's been written previously without losing its content?

Thank you in advance.

Answer 1

I'm the author of that module and unfortunately that isn't possible.

It is a planned feature, and (a small) part of the internal infrastructure is there to support it, but it isn't currently available and I can't say when it will be.

Update: this feature was never implemented and is no longer planned.

Answer 2

Another workaround is to use conditional_format, and use type='no_errors':

worksheet.conditional_format(your_range, {'type': 'no_errors',
                                          'format': your_format})

Answer 3

One way of doing that - using one wrapper method to write cell, and helper method to overwrite cell's value and style

import xlsxwriter

class XLSGenerator:
    def __init__(self):
        self.workbook = xlsxwriter.Workbook('file.xls')
        sheet1 = self.workbook.add_worksheet('sheet1')
        sheet2 = self.workbook.add_worksheet('sheet2')
        self.sheets = {'sheet1': sheet1, 'sheet2': sheet2}
        #  dictionary with all written cells
        self.written_cells = {sheet: {} for sheet in self.sheets}

    def write_cell(self, sheet_name, cell, value, cell_format_dict=None):
        """Writes value and style, and saves it in self.written_cells"""

        sheet = self.sheets[sheet_name]
        if cell_format_dict:
            cell_format = self.workbook.add_format(cell_format_dict)
            sheet.write(cell, value, cell_format)
        else:
            cell_format_dict = None
            sheet.write(cell, value)

        # save sheet_name, cell and cell_value, and cell_format (dict)
        # example ['sheet1']['C12'] = ('some_text', {'font_size': 14, 'bold': True}
        self.written_cells[sheet_name][cell] = (value, cell_format_dict)

    def apply_style(self, sheet_name, cell, cell_format_dict):
        """Apply style for any cell, with value or not. Overwrites cell with joined 
        cell_format_dict and existing format and with existing or blank value"""

        written_cell_data = self.written_cells[sheet_name].get(cell)
        if written_cell_data:
            existing_value, existing_cell_format_dict = self.written_cells[sheet_name][cell]
            updated_format = dict(existing_cell_format_dict or {}, **cell_format_dict)
        else:
            existing_value = None
            updated_format = cell_format_dict

        self.write_cell(sheet_name, cell, existing_value, updated_format)

Usage like this

generator = XLSGenerator()
generator.write_cell('sheet1', 'A1', '10')
generator.write_cell('sheet1', 'B2', '20')
generator.write_cell('sheet1', 'C3', '30')

table_borders = {"left": 1, 'right': 1, 'top': 1, 'bottom': 1}
for cell in ('A1', 'A2', 'A3', 'B1', 'B2', 'B3', 'C1', 'C2', 'C3'):
   generator.apply_style('sheet1', cell, table_borders)

generator.workbook.close()