class _Getch:

    """Gets a single character from standard input.  Does not echo to the screen."""

    def __init__(self):

        try:

            self.impl = _GetchWindows()

        except ImportError:

            try:

                self.impl = _GetchMacCarbon()

            except AttributeError:

                self.impl = _GetchUnix()

    def __call__(self): return self.impl()

class _GetchUnix:

    def __init__(self):

        import tty, sys, termios # import termios now or else you'll get the Unix version on the Mac

    def __call__(self):

        import sys, tty, termios

        fd = sys.stdin.fileno()

        old_settings = termios.tcgetattr(fd)

        try:

            tty.setraw(sys.stdin.fileno())

            ch = sys.stdin.read(1)

        finally:

            termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)

        return ch

class _GetchWindows:

    def __init__(self):

        import msvcrt

    def __call__(self):

        import msvcrt

        return msvcrt.getch()

class _GetchMacCarbon:

    """

    A function which returns the current ASCII key that is down;

    if no ASCII key is down, the null string is returned.  The

    page http://www.mactech.com/macintosh-c/chap02-1.html was

    very helpful in figuring out how to do this.

    """

    def __init__(self):

        import Carbon

        Carbon.Evt #see if it has this (in Unix, it doesn't)

    def __call__(self):

        import Carbon

        if Carbon.Evt.EventAvail(0x0008)[0]==0: # 0x0008 is the keyDownMask

            return ''

        else:

            #

            # The event contains the following info:

            # (what,msg,when,where,mod)=Carbon.Evt.GetNextEvent(0x0008)[1]

            #

            # The message (msg) contains the ASCII char which is

            # extracted with the 0x000000FF charCodeMask; this

            # number is converted to an ASCII character with chr() and

            # returned

            #

            (what,msg,when,where,mod)=Carbon.Evt.GetNextEvent(0x0008)[1]

            return chr(msg & 0x000000FF)

if __name__ == '__main__': # a little test

   print 'Press a key'

   inkey = _Getch()

   import sys

   for i in xrange(sys.maxint):

      k=inkey()

      if k<>'':break

   print 'you pressed ',k