title: How to force pandas to evaluate formulas of xlsx and not read them as NaN?
body: <p>Here are the things I am trying to do</p>
  
  <ol>
  <li>Read Excel file with formulas into pandas dataframe</li>
  <li>Change values in some cell </li>
  <li>Evaluate the cell values according to the formulas</li>
  <li>Finally, save that file as html</li>
  </ol>
  
  <p>Here's my code</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  from openpyxl import load_workbook
  
  wb = load_workbook(filename = 'initial.xlsx')
  sheet_names = wb.get_sheet_names()
  name = sheet_names[0]
  sheet_ranges = wb[name]
  df = pd.DataFrame(sheet_ranges.values)
  df['x']['C'] = 10
  df.to_excel("processing.xlsx", header=False, index=False)
  
  df1 = pd.read_excel("processing.xlsx", sheetname=0, header=0)
  df1.to_html('output.html')
  </code></pre>
  
  <p>With this code I am able to get fully functioning <strong>processing.xlsx</strong> but if I try to convert it into html the dataframe reads all formulas as <strong>NaN</strong>.  </p>
  
  <p><strong>Question</strong>: How to force pandas to evaluate formulas of xlsx and not read them as NaN?</p>
  
  <p>PS: If I try to convert initial.xlsx into html it works fine so something must be wrong in <strong>to_excel</strong> output.</p>