text: def read_input(fname):
      """Read txt file containing A DNA string."""
      with open(fname, 'r') as f:
          return f.read()
  
  
  def main_DNA(dna):
      """Counting the respective number of times that the symbols 'A', 'C', 'G', and 'T' occur in dna."""
      if len(dna) > 1000 or len(dna) <= 0:
          raise Exception('Input Error')
      dna_counts = map(dna.count, ['A', 'C', 'G', 'T'])
      return ' '.join(map(str, dna_counts))
  
  
  if __name__ == '__main__':
      dna = read_input('../datasets/DNA_1.txt')  # pragma: no cover
      print(main_DNA(dna))  # pragma: no cover
  