title: pandas add sql table, check if table exists
body: <p>I have this piece of code that loops for excel files in a directory, add the file in a sqlite db .
  I managed to get past the exception raised if the table exists but I find this inelegant and inefficient since the loop reads the excel file, add it in a Dataframe, etc...
  what ideally i would like is that I test the existence of the table before creating the df from excel.</p>
  
  <pre><code>response = {}
  for f in glob('T:\GESTION\toto\titi\tata\file_201*.xlsx'):
      print f
      datereg = re.search('T:\\\\GESTION\\\\toto\\\\titi\\\\tata\\\\file_(\d{4})(\d{2})(\d{2}).xlsx', f)
      if datereg is not None:
          dated = datetime.datetime(int(datereg.group(1)), int(datereg.group(2)), int(datereg.group(3)))
      print dated
  
      # ideally test if table in db exists here
  
      xl = pd.ExcelFile(f)
      df = xl.parse(sheetname="Sheet1")
      df = df[extractFields].drop_duplicates(subset='ISIN')
      df = df.set_index('ISIN', verify_integrity=True)
      response[dated] = df
      # print response
      engine = sqlalchemy.create_engine('sqlite:///my_db.sqlite')
      try:
          df.to_sql(dated.__str__(), engine, if_exists='fail')
      except ValueError as err:
          print(err)
          pass
  </code></pre>