old_contents: #!/usr/bin/env python
  
  '''
  Script: fy_print_seq_len_in_fasta.py
  Function: Print sequence length to STDOUT in fasta file
  Note: Python3 is not default installed for most computer, 
        and the extra-installed module like Biopython could
        not be directly used by python3. So, it's not the
        righ time to use Python3 now.
  Date: 2014/11/11
  '''
  
  import sys
  if len(sys.argv) < 2:
      print('Usage: ' + sys.argv[0] + ' <FASTA>')
      sys.exit()
  
  from Bio import SeqIO
  seqlen     = []
  num_of_seq = 0
  total_len  = 0
  for record in SeqIO.parse(sys.argv[1], 'fasta'):
      print("%s %i" % (record.id, len(record)))
      num_of_seq += 1
      total_len += len(record)
      seqlen.append(len(record))
  
  seqlen.sort()
  min_len = seqlen[0]
  max_len = seqlen[-1]
  
  print("Number of sequences: " + str(num_of_seq))
  print("Total length: " + str(total_len))
  print("Max length: " + str(max_len))
  print("Min length: " + str(min_len))
  
new_contents: #!/usr/bin/env python
  
  '''
  Script: fy_print_seq_len_in_fasta.py
  Function: Print sequence length to STDOUT in fasta file
  Note: Python3 is not default installed for most computer, 
        and the extra-installed module like Biopython could
        not be directly used by python3. So, it's not the
        righ time to use Python3 now.
  Date: 2014/11/11
  '''
  
  import sys
  if len(sys.argv) < 2:
      print('Usage: ' + sys.argv[0] + ' <FASTA>')
      sys.exit()
  
  from Bio import SeqIO
  seqlen     = []
  num_of_seq = 0
  total_len  = 0
  for record in SeqIO.parse(sys.argv[1], 'fasta'):
      print("%s %i" % (record.id, len(record)))
      num_of_seq += 1
      total_len += len(record)
      seqlen.append(len(record))
  
  seqlen.sort()
  min_len = seqlen[0]
  max_len = seqlen[-1]
  
  print('Number of sequences: ' + str(num_of_seq))
  print('Total length: ' + str(total_len))
  print('Max length: ' + str(max_len))
  print('Min length: ' + str(min_len))
  
subject: Use single quotes instead of double quotes