new_contents: #!/usr/bin/env python
  
  # Simulate the unix commands cd, ls, and pwd for non-Unix platforms (Pythonista for iOS)
  # Recommendation: paste the import plus 3 functions into the Python interactive prompt
  
  import os
  
  def cd(in_dir=os.path.expanduser('~')):
      os.chdir(in_dir)
      print(os.path.abspath(os.curdir))
  
  def ls(in_dir=os.curdir):
      print('\n'.join(os.listdir(in_dir)))
  
  def pwd():
      print(os.path.abspath(os.curdir))
  
  if __name__ == '__main__':
      pwd()
      ls()
      cd()
      pwd()
      ls()
      cd('Python')
      pwd()
      ls()
      cd('/')
      pwd()
      ls()
  
subject: Create cd_ls_pwd.py