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Groups > comp.lang.python > #92639

Re: Keypress Input

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On 2015-06-15, Oscar Benjamin <oscar.j.benjamin@gmail.com> wrote:

> Note that going into raw mode has other implications such as not
> being able to exit your program with ctrl-c or suspend with ctrl-z
> etc. You can explicitly process those kinds of contrl keys with
> something like:
>
> while True:
>     key = getch()
>     if 1 <= ord(key) <= 26:
>         ctrl_key = chr(ord(key) + 64)
>         print("ctrl-%c" % ctrl_key)
>         if ctrl_key == 'C':
>             break
>     else:
>         print("key: '%c'" % key)

It's probably better (at least on Linux) to just enable handling of
those characters in by setting the ISIG lflag:

    def getch():
        fd = sys.stdin.fileno()
        oldsettings = termios.tcgetattr(fd)
        try:
            tty.setraw(sys.stdin.fileno())
    
            # enable handling of ctrl-C, ctrl-Z, etc.            
            attr = termios.tcgetattr(fd)
            attr[3] |= termios.ISIG
            termios.tcsetattr(fd,termios.TCSANOW,attr)
    
            c = sys.stdin.read(1)
    
        finally:
            termios.tcsetattr(fd, termios.TCSADRAIN, oldsettings)
        return c

It would be a bit cleaner if the termios module supported the the
cfmakeraw(3) function, then you could do it this way and save a couple
of system calls:

    def getch():
        fd = sys.stdin.fileno()
        oldsettings = termios.tcgetattr(fd)
        try:
            newsettings = termios.makeraw(oldsettings)
            newsettings[3] |= termios.ISIG
            termios.tcsetattr(fd,termios.TCSANOW,newsettings)
            c = sys.stdin.read(1)
        finally:
            termios.tcsetattr(fd, termios.TCSADRAIN, oldsettings)
        return c

[I'm a bit surprised that after all these years using literal integers
to index into the attribute list is the "right" way.]
        
-- 
Grant Edwards               grant.b.edwards        Yow! Well, O.K.
                                  at               I'll compromise with my
                              gmail.com            principles because of
                                                   EXISTENTIAL DESPAIR!

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Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-03 18:22 +0000
  Re: Keypress Input Laura Creighton <lac@openend.se> - 2015-06-03 20:59 +0200
  Re: Keypress Input Gary Herron <gherron@digipen.edu> - 2015-06-03 12:15 -0700
  Re: Keypress Input Gary Herron <gherron@digipen.edu> - 2015-06-03 11:47 -0700
  Re: Keypress Input Laura Creighton <lac@openend.se> - 2015-06-04 12:50 +0200
  Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-06 18:28 +0000
    Re: Keypress Input Laura Creighton <lac@openend.se> - 2015-06-06 22:52 +0200
    Re: Keypress Input Chris Angelico <rosuav@gmail.com> - 2015-06-07 07:20 +1000
    Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-06-06 22:31 -0600
  Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-15 05:15 +0000
    Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-16 15:09 +0000
    Re: Keypress Input Christian Gollwitzer <auriocus@gmx.de> - 2015-06-19 07:20 +0200
      Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-20 14:59 +0000
      Re: Keypress Input Rick Johnson <rantingrickjohnson@gmail.com> - 2015-07-15 18:03 -0700
        Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-07-15 22:30 -0600
          Re: Keypress Input Rick Johnson <rantingrickjohnson@gmail.com> - 2015-07-16 10:22 -0700
            Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-07-16 15:27 -0600
        Re: Keypress Input Terry Reedy <tjreedy@udel.edu> - 2015-07-16 02:08 -0400
          Re: Keypress Input Rick Johnson <rantingrickjohnson@gmail.com> - 2015-07-16 11:30 -0700
        Re: Keypress Input Terry Reedy <tjreedy@udel.edu> - 2015-07-16 03:10 -0400
        Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-07-16 15:29 -0600
  Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-15 05:23 +0000
    Re: Keypress Input Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-06-15 12:22 +0100
      Re: Keypress Input Grant Edwards <invalid@invalid.invalid> - 2015-06-15 15:22 +0000
    Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-06-16 11:15 -0600
      Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-16 20:06 +0000
        Re: Keypress Input Grant Edwards <invalid@invalid.invalid> - 2015-06-16 20:49 +0000
          Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-06-16 19:22 -0600
          Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-06-18 16:42 -0600
      Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-06-20 15:02 +0000
        Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-06-20 10:30 -0600
  Re: Keypress Input Paul Rubin <no.email@nospam.invalid> - 2015-06-16 14:22 -0700
  Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-07-15 19:05 +0000
    Re: Keypress Input Michael Torrie <torriem@gmail.com> - 2015-07-15 13:17 -0600
      Re: Keypress Input John McKenzie <davros@bellaliant.net> - 2015-08-16 19:45 +0000

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