code: def read_knmi_dataset(directory):
      
      filemask = '%s*.txt' % directory
      filelist = glob.glob(filemask)
  
      columns_hourly = ['temp', 'precip', 'glob', 'hum', 'wind', 'ssd']
      ts = pd.DataFrame(columns=columns_hourly)
  
      first_call = True
      for file_i in filelist:
          print(file_i)
          current = read_single_knmi_file(file_i)
          if(first_call):
              ts = current
              first_call = False
          else:
              ts = pd.concat([ts, current])
      return ts
docs: Reads files from a directory and merges the time series
  
      Please note: For each station, a separate directory must be provided!
      data availability: www.knmi.nl/nederland-nu/klimatologie/uurgegevens
  
      Args:
          directory: directory including the files
  
      Returns:
          pandas data frame including time series