text: from io import BytesIO
  from lxml.etree import xmlfile
  import os
  from random import randint
  
  from openpyxl import Workbook
  from openpyxl.xml.functions import XMLGenerator
  
  def make_worksheet():
      wb = Workbook()
      ws = wb.active
      for i in range(1000):
          ws.append(list(range(100)))
      return ws
  
  
  def lxml_writer(ws=None):
      from openpyxl.writer.lxml_worksheet import write_rows
      if ws is None:
          ws = make_worksheet()
  
      out = BytesIO()
      with xmlfile(out) as xf:
          write_rows(xf, ws)
      #with open("lxml_writer.xml", "wb") as dump:
          #dump.write(out.getvalue())
      #ws.parent.save("lxml_writer.xlsx")
  
  
  def make_dump_worksheet():
      wb = Workbook(write_only=True)
      ws = wb.create_sheet()
      return ws
  
  def dump_writer(ws=None):
      if ws is None:
          ws = make_dump_worksheet()
      for i in range(1000):
          ws.append(list(range(100)))
  
  
  COLUMNS = 100
  ROWS = 1000
  BOLD = 1
  ITALIC = 2
  UNDERLINE = 4
  RED_BG = 8
  formatData = [[None] * COLUMNS for _ in range(ROWS)]
  
  def generate_format_data():
      for row in range(ROWS):
          for col in range(COLUMNS):
              formatData[row][col] = randint(1, 15)
  
  
  def styled_sheet():
      from openpyxl import Workbook
      from openpyxl.styles import Font, Style, PatternFill, Color, colors
  
      wb = Workbook()
      ws = wb.active
      ws.title = 'Test 1'
  
      red_fill = PatternFill(fill_type='solid', fgColor=Color(colors.RED), bgColor=Color(colors.RED))
      empty_fill = PatternFill()
      styles = []
      # pregenerate relevant styles
      for row in range(ROWS):
          _row = []
          for col in range(COLUMNS):
              cell = ws.cell(row=row+1, column=col+1)
              cell.value = 1
              font = {}
              fill = PatternFill()
              if formatData[row][col] & BOLD:
                  font['bold'] = True
              if formatData[row][col] & ITALIC:
                  font['italic'] = True
              if formatData[row][col] & UNDERLINE:
                  font['underline'] = 'single'
              if formatData[row][col] & RED_BG:
                  fill = red_fill
              cell.style = Style(font=Font(**font), fill=fill)
  
      #wb.save(get_output_path('test_openpyxl_style_std_pregen.xlsx'))
  
  
  def read_workbook():
      from openpyxl import load_workbook
      folder = os.path.split(__file__)[0]
      src = os.path.join(folder, "files", "very_large.xlsx")
      wb = load_workbook(src)
      return wb
  
  
  def rows(wb):
      ws = wb.active
      rows = ws.iter_rows()
      for r, row in enumerate(rows):
          for c, col in enumerate(row):
              pass
      print((r+1)* (c+1), "cells")
  
  
  def col_index1():
      from openpyxl.cell import get_column_letter
      for i in range(1, 18279):
          c = get_column_letter(i)
  
  
  
  """
  Sample use
  import cProfile
  ws = make_worksheet()
  cProfile.run("profiling.lxml_writer(ws)", sort="tottime")
  """
  
  
  if __name__ == '__main__':
      import cProfile
      ws = make_worksheet()
      #wb = read_workbook()
      #cProfile.run("rows(wb)", sort="tottime")
      #cProfile.run("make_worksheet()", sort="tottime")
      #cProfile.run("lxml_writer(ws)", sort="tottime")
      #generate_format_data()
      #cProfile.run("styled_sheet()", sort="tottime")
      #ws = make_dump_worksheet()
      #cProfile.run("dump_writer(ws)", sort="tottime")
      cProfile.run("col_index1()", sort="tottime")
  