title: Overwrite an excel sheet with pandas dataframe without affecting other sheets
body: <p>I want to overwrite an existing sheet in an excel file with Pandas dataframe but don't want any changes in other sheets of the same file. How this can be achieved.
  I tried below code but instead of overwriting, it is appending the data in 'Sheet2'.</p>
  <pre><code>import pandas as pd
  from openpyxl import load_workbook
  
  book = load_workbook('sample.xlsx')
  writer = pd.ExcelWriter('sample.xlsx', engine = 'openpyxl')
  writer.book = book
  writer.sheets = dict((ws.title, ws) for ws in book.worksheets)
  df.to_excel(writer, 'sheet2', index = False)
  writer.save()
  </code></pre>