Python function to get keypresses from the terminal

key_detect.py

def getchar():
   #Returns a single character from standard input
   import tty, termios, sys
   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
   
while 1:
    ch = getchar()
    print 'You pressed', ch

Good code. The only problem is that it traps everything - including control-Z, control-C, and anything else a user might invoke to force an interrupt signal.

insert following lines for easier testing ... now the loop breaks on every non-printable character

while 1:
    ch = getchar()
    if ch.strip() == '':
        print('bye!')
        break
    else:
        print 'You pressed', ch

My problem that it requires user to press something, I am looking for a code to return nothing if nothing has been pressed

ImportError: No module named termios

To handle Ctrl+C, and the windows imports:

def getchar():
	# Returns a single character from standard input
	import os
	ch = ''
	if os.name == 'nt': # how it works on windows
		import msvcrt
		ch = msvcrt.getch()
	else:
		import tty, termios, sys
		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)
	if ord(ch) == 3: quit() # handle ctrl+C
	return ch

while 1:
	ch = getchar()
	print 'You pressed %c (%i)' % (ch, ord(ch))

Good code. The only problem is that it traps everything - including control-Z, control-C, and anything else a user might invoke to force an interrupt signal.

if you use
tty.setcbreak() instead of tty.setraw()
linux will catch the control characters(like ctrl+c) but will still pass through keystrokes

@oname-15h, I find that KeyboardInterrupt at tty.setcbreak() crashes the BASH shell for some reason.

If tty.setraw() is used as before, then its capturing of all control characters makes the "try" block redundant, but if we want a way to return to the shell from within the getchar() routine, then we can test for ordinal values of the control codes and call sys.exit() if found.

def getchar():
    import tty, termios, sys
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    tty.setraw(sys.stdin.fileno())
    ch = sys.stdin.read(1)
    termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
    # Exit on ctrl-c, ctrl-d, ctrl-z, or ESC
    if ord(ch) in [3, 4, 26, 27]:
        sys.exit()
    return ch

The best solution on the internet so far, good job.
@jasonrdsouza Could i use this in a public script?
Thanks!

ty

Wouldn't it be better to move the imports outside the function body? That way the modules don't get imported every time the function is run but instead just once and then reused for every call to the function.