I have scripted code for writing pandas df into excel file with openpyxl. See Fill in pd data frame into existing excel sheet (using openpyxl v2.3.2).
from openpyxl import load_workbook
import pandas as pd
import numpy as np
writer.book = book
writer.sheets = dict((ws.title, ws) for ws in book.worksheets)
data_df.to_excel(writer, sheet_name="example", startrow=100, startcol=5, index=False)
I think you'll have to use
xlsxwriter doesn't support yet modifying of existing Excel XLSX files.