title: Add the existing column "References" to a new xlsx with the outputs
body: <p>I need some guidance here. I know that I'm probably making this too complex, but I'm quite new on the Python world. I'm learning and trying to do some useful stuff. So, this is my present task and issue:</p>
  
  <p>I have two xlsx files. Let's call them "New" and "Old". Both files have a column named "References" that work as unique IDs. </p>
  
  <p>I start to check if the References on the file "Old" are present on the file "New", so I can get all the "References" that were removed.</p>
  
  <p>After I check if the "References" on the file "New" are present on the file "Old" or not, so I can retrieve all the new references.</p>
  
  <p>Finally, I check if there was any changes on the column "Prices" of both files.</p>
  
  <p>With the new outputs I generate a new file that basically has 3 sheets with the result of each output. </p>
  
  <p>I'm near my goal, but I would like also to have the original column "References" in each new Sheet, so it would be easier to detect the changes. </p>
  
  <p>My description is sounding too confuse! But I hope that my code can help to understand what I want to do:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>import pandas as pd
  from pandas import ExcelWriter
  from pandas import ExcelFile
  pd.set_option('display.max_columns', 500)
  pd.set_option('display.max_rows', None)
  
  df = pd.ExcelFile('C:\\Users\\A\\Desktop\\Scraps\\cap_30_04t.xlsx')
  sheet1 = pd.read_excel(df, 'Antigo')
  sheet2 = pd.read_excel(df, 'Novo')
  
  nao_existe = sheet1['Ref'].isin(sheet2['Ref'])  #os falsos são os que não existem
  
  print(nao_existe)
  
  novos = sheet2['Ref'].isin(sheet1['Ref'])  #aqui os que derem Falso são os novos
  
  print(sheet2['Ref'], novos)
  
  precos = sheet2['Preço'].isin(sheet1['Preço'])  #ver se houve mudança de preço
  
  print(precos)
  
  
  # Create a Pandas Excel writer using XlsxWriter as the engine.
  writer = pd.ExcelWriter('C:\\Users\\Andre\\Desktop\\Scraps\\filename6.xlsx', engine='xlsxwriter')
  
  nao_existe.to_excel(writer, sheet_name='nao_existe')
  novos.to_excel(writer, sheet_name='novos')
  precos.to_excel(writer, sheet_name='preco')
  
  # Close the Pandas Excel writer and output the Excel file.
  writer.save()</code></pre>
  </div>
  </div>
  </p>