all_data = pd.DataFrame()

  for filename in all_files:
    df = pd.read_csv(filename, index_col='Date', header=0)
    all_data = pd.concat([all_data, df], axis=0)
    
    print(f'size before: {len(df.index)}')
    # Remove dupli
    # https://stackoverflow.com/questions/13035764/remove-pandas-rows-with-duplicate-indices/14900065#14900065
    df = df[~df.index.duplicated(keep='first')]
    #
    df.to_csv("filename.csv", index = False, header=True)