title: Using Python to populate data to existing excel file
body: <h1>What I'm trying to do:</h1>
  
  <p>I'm using Python to populate data to an existing Excel file.</p>
  
  <h1>What works:</h1>
  
  <p>My code below is successful in exporting the table to Excel file "Futures.xls". </p>
  
  <h1>What doesn't work:</h1>
  
  <p>The code below extracts table from website and exports to Futures excel file ( 100 Rows )The subsequent code re-opens Futures file and appends to Futures1 excel file ( 200 Rows ). However, if I continue to the run the subsequent code multiple times I cannot get more than 200 rows like 300 rows and so on as an when I run the code. Can someone tell me the issue?  </p>
  
  <h1>My code:</h1>
  
  <pre class="lang-py prettyprint-override"><code>from urllib.request import urlopen
  from bs4 import BeautifulSoup
  import requests
  import pandas as pd
  from pandas import ExcelWriter
  from pandas import ExcelFile
  import os
  
  url = "https://quotes.ino.com/exchanges/contracts.html?r=NYMEX_NG"
  res = requests.get(url)
  soup = BeautifulSoup(res.text, 'lxml')
  
  Markets = []
  Contracts =[]
  Opens =[]
  Highs =[]
  Lows =[]
  Lasts=[]
  Changes=[]
  Pcts=[]
  
  data_rows = soup.findAll('tr')[3:]
  
  for td in data_rows[:100]:
      Market = td.findAll ('td')[0].text
      Markets.append(Market)
      Contract = td.findAll('td')[1].text
      Contracts.append(Contract)
      Open = td.findAll('td')[2].text
      Opens.append(Open)
      High = td.findAll('td')[3].text
      Highs.append(High)
      Low = td.findAll('td')[4].text
      Lows.append(Low)
      Last = td.findAll('td')[5].text
      Lasts.append(Last)
      Change = td.findAll('td')[6].text
      Changes.append(Change)
      Pct = td.findAll('td')[7].text
      Pcts.append(Pct)
      Time = td.findAll('td')[8].text
  
      df = pd.DataFrame({'Contracts' :Contracts, 'Markets':Market,'Open':Opens, 'High':Highs, 'Low':Lows,'Last':Lasts,'Pct':Pcts})
  
      out_path = "C:\Sid\Futures.xls"
      writer = pd.ExcelWriter(out_path , engine='xlsxwriter')
      df.to_excel(writer,'Sheet2',index=False)
      writer.save()
  
      from openpyxl import load_workbook
      from openpyxl.utils.dataframe import dataframe_to_rows
  
      wb = load_workbook("C:\Sid\Futures.xlsx")
      ws = wb['Sheet2']
  
      from openpyxl import load_workbook
      from openpyxl.utils.dataframe import dataframe_to_rows
  
      wb = load_workbook("C:\Sid\Futures.xlsx")
      ws = wb['Sheet2']
  
      for row in dataframe_to_rows(df, header=None, index = True):
      ws.append(row)
      wb.save('C:\Sid\Futures1.xlsx')
  </code></pre>
  
  <h1>Additional:</h1>
  
  <p>Also, what code do I need so that my python runs automatically when my website updates? Prices change every 15 minutes.</p>