title: how to make a pandas take values from multiple lists within a list
body: <p>I have a folder with multiple html files.I want the code to go through each and every file and pick the subject verb object triplets using nlp.  I then want pandas to list all of them under the headings of subject verb object for all the files together in one data frame. The problem I face is panda lists only the the subject verb object from the last file and not the first two. When I print the sub_verb_obj in loop it shows 3 lists within a list. But pandas does not pick the 3 lists triplets. Can someone tell me what mistake am I doing?</p>
  <pre><code>
  sub_verb_obj=[]
  folder_path = 'C:/Users/user3/.ipynb_checkpoints/xyz/xyz_2018'
  for filename in glob.glob(os.path.join(folder_path, '*.html')):
    with open(filename, 'r',encoding='utf-8') as f:
      pat = f.read()
      
      doc=nlp(text)
      text_ext = textacy.extract.subject_verb_object_triples(doc)
      sub_verb_obj=list(text_ext)
      
  sao=pd.DataFrame(sub_verb_obj)
  sao.columns=['subject','verb','object']
  sao=sao.set_index('subject')
  print(sao)```
  
  how can I make sure the pandas lists all the subject verb object from all the files in a folder in a single dataframe?
  </code></pre>