XLS support

[danilke]

Hi, I noticed, that this repo has pull request #29 with xls support. But there is some little problem with testing. Is some hope that it will be merged? Thanks.

[masterfloda]

I wrote my own ExcelRenderer based on openpyxl (though no tests yet and I only tried it with Python 3.6 and Django 1.11):

from six import BytesIO
from openpyxl import Workbook
from rest_framework_csv.renderers import CSVRenderer


class ExcelRenderer(PaginatedCSVRenderer):
    media_type = 'application/ms-excel'
    format = 'xlsx'
    results_field = 'results'

    def render(self, data, media_type=None, renderer_context=None, writer_opts=None):
        """
        Renders serialized *data* into an Excel sheet

        Args:
            data (list): data to be rendered
            media_type (str): ContentType
            renderer_context (dict): context containing header, label, encoding etc.
            writer_opts (dict):

        Returns:
            str: rendered data
        """
        # no data received
        if data is None:
            return ''

        # might be a paginated list
        if isinstance(data, dict) and self.results_field in data:
            data = data[self.results_field]

        # data is not a list
        if not isinstance(data, list):
            data = [data]

        header = renderer_context.get('header', self.header)
        labels = renderer_context.get('labels', self.labels)

        # build the table
        table = self.tablize(data, header=header, labels=labels)

        # create a workbook with a worksheet
        workbook = Workbook()
        worksheet = workbook.active

        # go through the table and create the excel sheet
        for row_idx, row in enumerate(table, 1):
            for col_idx, elem in enumerate(row, 1):
                # empty values are empty strings
                if elem is None:
                    elem = ''
                # format numbers as numbers and not strings
                try:
                    elem = float(elem)
                except ValueError:
                    elem = str(elem)

                # create the cell
                worksheet.cell(column=col_idx, row=row_idx, value=elem)

        # save the sheet to the buffer
        output_buffer = BytesIO()
        workbook.save(output_buffer)

        return output_buffer.getvalue()

and in my viewset I have this method:

    def finalize_response(self, request, response, *args, **kwargs):
        """ add content-disposition header to CSV and XLS rendered files

        gets executed at the very end of the ViewSet rendering

        Args:
            request (HTTPRequest): request object
            response (Response): finalized response

        Returns:
            Response: Response containing content-disposition header for file renderers
        """
        super(AbstractBaseViewSet, self).finalize_response(request, response, *args, **kwargs)

        file_renderers = ('csv', 'xlsx')
        """renderers that return files and should be an attachment with a filename"""

        # this renderer should download a file
        if response.accepted_renderer.format in file_renderers:
            filename = 'export'
            # add a timestamp
            filename += '_' + datetime.now().strftime('%Y-%m-%d_%H%M%S')
            # file extension
            filename += '.' + response.accepted_renderer.format
            # add the header
            response['content-disposition'] = 'attachment; filename=' + filename

        return response

[danilke]

@masterfloda Nice! Thank you for feedback!