title: Multi index frame in Python-pandas
body: <p>Thanks in advance for the help.</p>
  <p>I am trying to program a web scraper to collect data from a website. I try to save that data in a frame. However every time the scraper changes the page it write again the dataframe and does not save the previous info collected.</p>
  <p>Any ideas how to solve this?</p>
  <pre><code>   j=1
      i=0
      try:  
          url_next = str('https://www.viamichelin.es/web/Restaurantes/Restaurantes-Espana?page='+str(j))
          print(url_next)
          while(url_next is not None):
              url_next = str('https://www.viamichelin.es/web/Restaurantes/Restaurantes-Espana?page='+str(j))
              fetchURL(url_next)
              print (url_next)           
              data = pd.DataFrame({'site':'MICHELIN','name': '', 'pdv_url': '', 'rating': '','address' : '','web' : '','phone' : '','map' : '','email' : '','id' : '', 'datetime' : ''}, index = [j,i])
              i=0
              url=url_next
              while(url is not None):
        
                      html = fetchURL(url_next)
                      soup = BeautifulSoup(html, &quot;html.parser&quot;)
    
                      card_list = soup.find_all(&quot;li&quot;, class_=&quot;poi-item-restaurant&quot;)
                      # print(card_list)
    
                      for card in card_list[0:len(card_list)]:
                         # card =card_list[0]                
                          name = card.find('div','poi-item-name truncate').get_text('title')
                          pdv_url = url_next+card.find('a').get('href')
                          html = fetchURL(pdv_url)
                          soup = BeautifulSoup(html, &quot;html.parser&quot;)
                          #dataOutput = {'site':'MICHELIN','pdv_data':{'name': name, 'pdv_url': pdv_url, 'rating': str(rating)}}
                          #print(json.dumps(dataOutput))
                          #pdv_data = pd.DataFrame({'name': name, 'pdv_url': pdv_url, 'rating': str(rating)},index = [0])
                          data.iloc[i]['name'] = name
                          data.iloc[i]['pdv_url'] = pdv_url                         
                          i=i+1
                          print(data)
                          data = data.append(pd.DataFrame({'site':'MICHELIN','name': '', 'pdv_url': '', 'rating': '','address' : '','web' : '','phone' : '','map' : '','email' : '','id' : '', 'datetime' : ''}, index = [j,i]), ignore_index = True)
                      # print(soup)
                      # address = re.sub('  +','',soup.find(class_='address-t-record').get_text().replace('\n', '').replace('Ver mapa',''))
                      # print(soup.find('div', class_='highlighted-box-right').find_all('p'))
                      # ficha = soup.find('div', class_='tab-container bb-tab-container active').find_all('div', class_='data')
                      # for campo in ficha:
                      #     print(campo.find('span',class_='first').get_text())
                
                      # price = soup.find_all(class_='right').get_text()
                      # price_menu = soup.find_all(class_='right').get_text()
                
                      url = None
                      # print(name)
              j=j+1
      except AttributeError:
          url_next = None
  </code></pre>