new_contents: def read_file(filename):
      # Open the file
      file_obj = open(filename)
  
      # Iterate over lines in the file
      for line in file_obj:
  
          # Split line by spaces (creates a list)
          # Alternatives: split(',')
          numbers = line.split()
  
          if len(numbers) != 2:
              # Convert strings to numbers
  
              numbers2 = []
              for number in numbers:
                  # Convert number to float
                  number = float(number)
  
                  # Append to temperary list
                  numbers2.append(number)
  
              # Replace numbers by numbers2
              numbers = numbers2
  
          else:
              # We're processing a header
              print 'Skipping header line'
  
      return contents
  
  # Just for debugging purposes
  read_file('data.txt')
  
subject: Convert list, for later reference.