text: #!/usr/bin/env python
  
  import sys
  import os
  import os.path as op
  import subprocess
  
  num = sys.argv[1]
  dirname = (d for d in os.listdir('demos') if d.startswith(num)).send(None)
  dirname = op.join('demos', dirname)
  print(dirname)
  
  cmd = ['python', 'demo.py']
  env = os.environ.copy()
  env['PYTHONPATH'] = op.dirname(op.abspath(__file__))
  try:
      subprocess.call(cmd, cwd=dirname, env=env)
  except KeyboardInterrupt:
      pass
  