Curing Python's Neglect

Re:Curing Python's Neglect by derefr on Saturday May 30, 2009 @03:28AM (#633370)

But how does "exit" by itself print that pretty little message telling you that, although it's obvious you wanted to exit, it's not going to let you? It's not just a function reference if it shows up that way.

[ Parent | on HN ]

Re:Curing Python's Neglect by anuraggoel on Saturday May 30, 2009 @04:14AM (#633414)

http://docs.python.org/library/constants.html#exit

In CPython, exit is actually an object of type site.Quitter (the actual class is implementation dependent). site.Quitter overrides the __repr__ special method (which is called by the interpreter on any expression typed in the shell to print the result). site.Quitter also overrides the __call__ special method, so when an object of type site.Quitter is called, the overridden __call__ method invokes system exit.

   >>> exit_class = type(exit) #gets a reference to the class
   >>> my_exit = exit_class('bye') #the arg is used to print the message
   >>> my_exit
   Use bye() or Ctrl-D (i.e. EOF) to exit
   >>> my_exit()
   <python shell exits>

Minor inconsistency: typing "bye()" doesn't work so technically the message is incorrect. But I suppose they don't want you to be hacking exit() in the first place.

[ Parent | on HN ]

Re:Curing Python's Neglect by ii on Saturday May 30, 2009 @06:15AM (#633487)

  >>> class ExitFunc:
  ...   def __call__(self): __builtins__.exit()
  ...   def __repr__(self): return "That's how!"
  ...
  >>> exit = ExitFunc()
  >>> exit
  That's how!
  >>> exit()

[ Parent | on HN ]