title: xlsxwriter chart grid spacing
body: <p>I'm currently trying to create charts in excel via the xlsxwriter python module. I've gotten it to graph just fine, however I'm trying to get it to look nice. I've been able to add major and minor gridlines, change their line width, and dash type, but I can't figure out how to modify their spacing. (e.g., minor lines on every unit with major lines on every 5 units)</p>
  
  <p>As far as I can tell, it's not an option, but I thought I'd throw this out there to see if an expert had a trick (I've just started using this module) and/or put this out there for people looking for this option in the future.</p>
  
  <p>Here's the code I'm working with right now:</p>
  
  <pre><code>chart = wb.add_chart({'type': 'line'})
  chart.add_series({
      'name': 'Sheet1!{:}'.format(xlsxwriter.utility.xl_rowcol_to_cell(0, data_column)),
      'categories': ['Sheet1', 1, time_column, num_of_data_pts, time_column],
      'values': ['Sheet1', 1, i, num_of_data_pts, data_column],
      'line': {'color': 'blue'},
  })
  chart.set_x_axis({
      'num_font': {'italic': True},
      'major_gridlines': {
          'visible': True,
          'line': {'width': 1}
      },
      'minor_gridlines': {
          'visible': True,
          'line': {'width': 1, 'dash_type': 'dash'}
      },
  })
  chart.set_legend({'position': 'none'})
  ws.insert_chart(5, 5, chart)
  </code></pre>
  
  <p>Also I've tried using the 'major_unit' attribute, but it appears that is something to do with if the x axis is a date only.</p>