Flask xlsx writer

flask_xlsxwriter.py

from flask import  Response
import StringIO, mimetypes
import xlsxwriter
from datetime import datetime 
from werkzeug.datastructures import Headers

def xlsx_export():
    try:
        # Flask response
        response = Response()
        response.status_code = 200

        # Create an in-memory output file for the new workbook.
        output = StringIO.StringIO()

        # Craete workbook
        workbook = xlsxwriter.Workbook(output, {'in_memory': True})
        worksheet = workbook.add_worksheet('hello')

        # Write some test data.
        worksheet.write(0, 0, 'Hello, world!')

        # Close the workbook before streaming the data.
        workbook.close()

        # Rewind the buffer.
        output.seek(0)

        # Add output to response
        response.data = output.read()

        # Set filname and mimetype
        file_name = 'export_{}_{}.xlsx'.format('this_awesome', datetime.now())
        mimetype_tuple = mimetypes.guess_type(file_name)

        # HTTP headers for forcing file download
        response_headers = Headers({
                'Pragma': "public",  # required,
                'Expires': '0',
                'Cache-Control': 'must-revalidate, post-check=0, pre-check=0',
                'Cache-Control': 'private',  # required for certain browsers,
                'Content-Type': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
                'Content-Disposition': 'attachment; filename=\"%s\";' % file_name,
                'Content-Transfer-Encoding': 'binary',
                'Content-Length': len(response.data)
            })

        if not mimetype_tuple[1] is None:
            response.update({
                    'Content-Encoding': mimetype_tuple[1]
                })

        # Add headers
        response.headers = response_headers

        #jquery.fileDownload.js requirements
        response.set_cookie('fileDownload', 'true', path='/')

        # Return the response
        return response

    except Exception as e:
        print(e)

Thanks for your gist.
I had to change:
output = StringIO.StringIO()
to
output = BytesIO()
but now always works great.

i don't think mimetype is needed here when we know what the content-type should be, and the file isn't encoded.

also the Cache-Control header is overwritten here (it's used as a key twice in the dictionary), also according to this post:
https://stackoverflow.com/questions/34663916/are-cache-control-pre-check-and-post-check-headers-still-supported-by-ie
pre-check / post-check headers don't need to be used