Check for keystroke

[Brian]

Inside a loop, I need to passively check to see if a key is pressed or not
without pausing like raw_input does. Some pseudocode:

While true:
If a key is pressed
which key is pressed

do other stuff inside loop


Google groups turned up this thread:

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&safe=off&th=
3221aa1ee6ef2ec2&seekm=2259b0e2.0307310800.3310ec83%
40posting.google.com&frame=off

TinyURL: http://tinyurl.com/4chqh


But neither the pygame or curses solution worked. Any new thoughts on
this?

 

[Brian]

Also, this is being done in Linux and does NOT need to be multi-OS
compatible.

 

[Josef Meile]

Hi Brian,

I saw an example on pyserial called "miniterm.py". It was about doing a
text based chat between two computers connected with through the serial
port. It is made with threads, so you can do something else while it
waits for characters from the keyboard. When a key is pressed, then it
is echoed to the console. I think you can easilly remove the serial
stuff and do the check you need. Here is the link:

http://cvs.sourceforge.net/viewcvs.py/pyserial/pyserial/examples/miniterm.py

Regards,
Josef

 

[Lee Phillips]

Inside a loop, I need to passively check to see if a key is pressed or not
without pausing like raw_input does.

I've had partial success on Mac OS X using termios (partial because
it seems to miss some keystrokes - also I haven't looked at this in
a while):

import termios
# in your method:
old = termios.tcgetattr(fd) # Old term info for restoration later
new = termios.tcgetattr(fd)
new[3] = new[3] & ~termios.ICANON & ~termios.ECHO
new[6][termios.VMIN] = 1
new[6][termios.VTIME] = 0
termios.tcsetattr(fd, termios.TCSANOW, new)

while 1:
try:
command = os.read(fd, 1)
print command+">", #Echo manually
if command == '0':
termios.tcsetattr(fd, termios.TCSADRAIN, old) #Terminal back to line mode
break
elif command == 'b':
# do something....
# and so on.....
finally:
termios.tcsetattr(fd, termios.TCSAFLUSH, old)

 

[Brian]

It took a little bit of coaxing, but I finally got it to run.
Unfortunately, it still pauses while waiting for a keystroke. Am I
missing something?

Fixed code:
import termios, sys, os
fd = sys.stdin.fileno()
old = termios.tcgetattr(fd) # Old term info for restoration later
new = termios.tcgetattr(fd)
new[3] = new[3] & ~termios.ICANON & ~termios.ECHO
new[6][termios.VMIN] = 1
new[6][termios.VTIME] = 0
termios.tcsetattr(fd, termios.TCSANOW, new)

while 1:
try:
command = os.read(fd, 1)
print command+">", #Echo manually
if command == 'p':
termios.tcsetattr(fd, termios.TCSADRAIN, old)
#Terminal back to line mode
break
finally:
termios.tcsetattr(fd, termios.TCSAFLUSH, old)

 

[Brian]

stdscr.nodelay(1)

Gah, I'm a retard.

 

[Lee Phillips]

It took a little bit of coaxing, but I finally got it to run.
Unfortunately, it still pauses while waiting for a keystroke. Am I
missing something?

No, I am - I didn't pay enough attention to what you said you wanted.

 

[Mike Meyer]

stdscr.nodelay(1)

Gah, I'm a retard.

Another good option is select.poll() or select.select().

<mike