title: How to replace specific words in specific column with another from excel
body: <ul>
  <li>I've problem with replacing, here's what I wrote, I need to replace 1999 with 1900 as you can see. I started recently, so please excuse me. (I searched a lot and watched clips on YouTube, but the method didn't work.)</li>
  </ul>
  
  <pre><code>        import pandas as pd
          df = pd.read_excel('book1.xlsx')
  
          #replace
          df.replace("1999","1900")
  
          #I also tried this method, but it didn't work.
          #df.replace(to_replace = "1999", value = "1900")
  
          #writer
          writer = pd.ExcelWriter('book2.xlsx')
          df.to_excel(writer,'new_sheet')
          writer.save()
  </code></pre>
  
  <hr>
  
  <ul>
  <li>My second question, how can I replace data through a text file (or Excel), for example, replace 1999 (in column A, book1.xlsx) with the column b in mistakes.xlsx.</li>
  </ul>
  
  <pre><code> A     B
   1999   1900
  </code></pre>
  
  <p>Thank you guys for the help.</p>