title: Getting the columns messed up after pd.concat Pandas
body: <p>I am trying to concatenate some dataframes but I getting the wrong order of columns after done.</p>
  
  <p>My code is:</p>
  
  <pre><code>def numOfDays(date1, date2): 
  return (date2-date1).days
  
  first_case_report = datetime.strptime('22-01-2020', '%d-%m-%Y')
  NumOfdays_reported = numOfDays(first_case_report, datetime.today())
  
  column_names = ['Province/State','Country/Region','Last Update','Confirmed','Deaths','Recovered']
  df = pd.DataFrame(columns = column_names)
  df.to_csv(index=True)
  
  df.head()
  Output:
      Province/State  Country/Region  Last Update Confirmed   Deaths  Recovered
  
  ind = 0
  while ind &lt; NumOfdays_reported:
      date_report = (pd.Timestamp(first_case_report) + pd.DateOffset(days=ind)).strftime('%m-%d-%Y')
      url = "https://raw.githubusercontent.com/CSSEGISandData/COVID-19/master/csse_covid_19_data/csse_covid_19_daily_reports/{0}.csv".format(date_report)
      source = pd.read_csv(url,index_col=0,parse_dates=[0])
  
      df = pd.concat([df,source], sort=True)
      ind += 1   
  
  df.head()
  Output:
  Confirmed   Country/Region  Deaths  Last Update Latitude    Longitude   Province/State  Recovered
  </code></pre>
  
  <p>The last df.head() shows that the columns are messed up, for example compare the column Province/State with the df.head() executed, why is that happening?</p>
  
  <p>Any ideas would be highly appreciated.</p>
  
  <p>Thanks a lot beforehand.</p>