old_contents: #!/usr/bin/env python3
  
  import hashlib
  import sys
  
  for path in sys.argv[1:]:
      for ext, hash in [('sha256', hashlib.sha256), ('sha512', hashlib.sha512)]:
          written = '{}.{}'.format(path, ext)
          with open(path, 'rb') as fin, open(written, 'w') as fout:
              digest = hash(fin.read()).hexdigest()
              print('{} *{}'.format(digest, path), file=fout)
  
new_contents: #!/usr/bin/env python3
  """Writes SHA-256 and SHA-512 hashes of files passed as arguments"""
  
  import hashlib
  import sys
  
  for path in sys.argv[1:]:
      for ext, hash in [('sha256', hashlib.sha256), ('sha512', hashlib.sha512)]:
          written = '{}.{}'.format(path, ext)
          with open(path, 'rb') as fin, open(written, 'w') as fout:
              digest = hash(fin.read()).hexdigest()
              print('{} *{}'.format(digest, path), file=fout)
  
subject: add module-level docstring