Develop Reference

Stopping a python program when an arbitrary key was pressed while the program is running

I recently got to know about the python module signal. With that, we can capture a SIGINT and do what we want after capturing it. I used it as below. In that case I am just using SIGINT to print that program is going to be stopped and stop the program.
import signal
import os
import time
def signalHandler(signalnumb, frame):
print("Signal Number:", signalnumb, " Frame: ", frame)
print('Exiting the program...')
os._exit(0)
signal.signal(signal.SIGINT, signalHandler)
c=0
# Loop infinite times using the while(1) which is always true
while 1:
print(c)
#sleep for 1 seconds using the sleep() function in time
time.sleep(1)
c=c+1
Now I want to give any signal from keyboard(for example pressing 'q') and as soon as signal was recieved, the python program should be stopped. Has anyone got some experience on how to do that? Any other method rather than using signal module (for example using multithreading) is accepted.
Edit1-
Later I tried to use pynput module as suggested in one of a similar kind of question. For sure I have done a mistake. It doesn't work as I expected. It means with a key press, I couldn't stop the for loop from running.
from pynput import keyboard
import time
def on_press(key):
for i in range(100):
print(i)
time.sleep(1)
if key == keyboard.Key.esc:
return False # stop listener
try:
k = key.char # single-char keys
except:
k = key.name # other keys
if k in ['1', '2', 'left', 'right']: # keys of interest
# self.keys.append(k) # store it in global-like variable
print('Key pressed: ' + k)
return False # stop listener; remove this if want more keys
listener = keyboard.Listener(on_press=on_press)
listener.start() # start to listen on a separate thread
listener.join() # remove if main thread is polling self.keyspython
Can someone point out how to do it using pynput in correct way?

This was my original implementation:
a = input('Press a key to exit')
if a:
exit(0)
However, it seems that you need a piece of code that will allow for any key to be clicked and immediately exit out of the program, without hitting enter afterwards. This may be a better way to do that:
import readchar
print("Press Any Key To Exit")
k = readchar.readchar()
Hope this helps!

After carefully understanding about the threads and pynput module, I managed to stop a for loop (or any program which runs as a separate thread) using a key press callback.
from pynput import keyboard
import os
import threading
import time
loop_running = False
def on_press(key):
print(dir(key))
global loop_running
#if key == keyboard.Key.delete and not loop_running:
if ('char' in dir(key)) and (key.char == 's') and (not loop_running):
t=threading.Thread(target=start_loop)
t.start()
#elif key==keyboard.Key.tab: #if this is used, the attributes related to 'key' will be changed. you can see them since I have used a print(dir(key))
elif key.char == 'q':
loop_running=False
def start_loop():
global loop_running
loop_running = True
for i in range(100):
if not loop_running:
os._exit(0)
print(i)
time.sleep(1)
with keyboard.Listener(on_press=on_press) as listner:
listner.join()

how to dont close python console after printing something

I have a code that print something in the console and after some works it clear console and print something new
so putting input() not works for me cause then it will wait user to do something but I want this printing stuff continue
how should I do it?
my code is exctracting a zip file and in the same time printing how much of it is done
import threading
def Ex():
from zipfile import ZipFile
with ZipFile(my zip file) as zf:
zf.extractall(path,pwd=my password)
def loading():
done=False
f=[]
T=time.time()
while not done:
try:
f=os.listdir(my path)
clearConsole = lambda: os.system('cls' if os.name in ('nt', 'dos') else 'clear')
clearConsole()
print('Installing resources : '+str(int(len(f)/25*100))+'%')
except:
pass
if len(f)==25:
done=True
time.sleep(5)
time.sleep(10)
sys.exit()
threading.Thread(target=Ex).start()
threading.Thread(target=loading).start()

If you want to move the cursor to the first of line, use \r.
f = os.listdir("path/to/file")
print('Installing resources : '+str(int(len(f)/25*100))+'%', end='\r')
os.system does not run the commend in the current shell. It opens a new one. So you are just clearing a new shell every 5 seconds. If you really want to hold that, you can use pause command in Windows, which waits for user input and then close it. (cls; pause)

Python Block Keyboard / Mouse Input

i am currently trying to write a short script that will rickroll (open a youtube link) while the user is watching and can't interfere.
I have managed to open insert the link slowly letter by letter and am now trying to block user inputs.
I have tried using the ctypes import to block all inputs, run the script and then unblock again, but it somehow won't block the input. I'm just receiving my RuntimeError message.
How do i fix it, so the inputs get blocked?
Thanks in advance!
Heres the code:
import subprocess
import pyautogui
import time
import ctypes
from ctypes import wintypes
BlockInput = ctypes.windll.user32.BlockInput
BlockInput.argtypes = [wintypes.BOOL]
BlockInput.restype = wintypes.BOOL
blocked = BlockInput(True)
if blocked:
try:
subprocess.Popen(["C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe",])
time.sleep(3)
pyautogui.write('www.youtube.com/watch?v=DLzxrzFCyOs', interval= 0.5)
pyautogui.hotkey('enter')
finally:
unblocked = BlockInput(False)
else:
raise RuntimeError('Input is already blocked by another thread')

You can use the keyboard module to block all keyboard inputs and the mouse module to constantly move the mouse, preventing the user from moving it.
See these links for more details:
https://github.com/boppreh/keyboard
https://github.com/boppreh/mouse
This blocks all the keys on the keyboard (the 150 is large enough to ensure all keys are blocked).
#### Blocking Keyboard ####
import keyboard
#blocks all keys of keyboard
for i in range(150):
keyboard.block_key(i)
This effectively blocks mouse-movement by constantly moving the mouse to position (1,0).
#### Blocking Mouse-movement ####
import threading
import mouse
import time
global executing
executing = True
def move_mouse():
#until executing is False, move mouse to (1,0)
global executing
while executing:
mouse.move(1,0, absolute=True, duration=0)
def stop_infinite_mouse_control():
#stops infinite control of mouse after 10 seconds if program fails to execute
global executing
time.sleep(10)
executing = False
threading.Thread(target=move_mouse).start()
threading.Thread(target=stop_infinite_mouse_control).start()
#^failsafe^
And then your original code here (the if statement and try/catch block are no longer necessary).
#### opening the video ####
import subprocess
import pyautogui
import time
subprocess.Popen(["C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe",])
time.sleep(3)
pyautogui.write('www.youtube.com/watch?v=DLzxrzFCyOs', interval = 0.5)
pyautogui.hotkey('enter')
#### stops moving mouse to (1,0) after video has been opened
executing = False
Just a few notes:
The mouse-moving is hard to stop from outside of the program (it's basically impossible to close the program when it is executing, especially as the keyboard is also being blocked), that's why I put in the failsafe, which stops moving the mouse to (1,0) after 10 seconds.
(On Windows) Control-Alt-Delete does allow Task Manager to be opened and then the program can be force-stopped from there.
This doesn't stop the user from clicking the mouse, which can sometimes prevent the YouTube link from being typed in full (i.e. a new tab can be opened)
See a full version of the code here:
https://pastebin.com/WUygDqbG

you could do something like this to block both keyboard and mouse input
from ctypes import windll
from time import sleep
windll.user32.BlockInput(True) #this will block the keyboard input
sleep(15) #input will be blocked for 15 seconds
windll.user32.BlockInput(False) #now the keyboard will be unblocked

Here's a function for blocking keyboard and mouse input. You can pass a number to the blockMouseAndKeys function to adjust the timeout period:
import os
import time
import pyautogui
from threading import Thread
from keyboard import block_key
def blockMouseAndKeys(timeout=5):
global blocking
blockStartTime = time.time()
pyautogui.FAILSAFE = False
blocking = True
try: float(timeout)
except: timeout = 5
def blockKeys(timeout):
global blocking
while blocking:
if timeout:
if time.time()-blockStartTime > timeout:
print(f'Keyboard block timed out after {timeout}s.')
return
for i in range(150):
try: block_key(i)
except: pass
def blockMouse(timeout):
global blocking
while blocking:
def resetMouse(): pyautogui.moveTo(5,5)
Thread(target=resetMouse).start()
if timeout:
if time.time()-blockStartTime > timeout:
print(f'Mouse block timed out after {timeout}s.')
return
def blockTimeout(timeout):
global blocking
time.sleep(timeout)
blocking = False
pyautogui.FAILSAFE = False
print('Done blocking inputs!')
print('Blocking inputs...')
Thread(target=blockKeys, args=[timeout]).start()
Thread(target=blockMouse, args=[timeout]).start()
Thread(target=blockTimeout, args=[timeout]).start()
blockMouseAndKeys(timeout=10)
os.startfile('https://www.youtube.com/watch?v=DLzxrzFCyOs')

Multimedia Keys in Python (Linux)

I want to detect when the XF86Launch1 key is pressed on my keyboard, using Python.
I have a headless server with a Bluetooth connected keyboard. I'd like to launch a command-line program whenever a specific multimedia key is pressed.
At the moment, I'm using:
import sys
import tty, termios
def getch():
fd = sys.stdin.fileno()
old_settings = termios.tcgetattr(fd)
try:
tty.setraw(fd)
ch = sys.stdin.read(1)
finally:
termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
return ch
print getch()
But it won't detect multimedia keys. Nothing prints out when I press them.
Is there a way to detect these keys on a headless Ubuntu box - or a better way to launch a program on keypress?

Rather than trying to read stdin of the tty, you can use linux's input device api to read them.
On linux, all input devices show up as a file under /dev/input (such as /dev/input/event0) and when one read()s from these files, structured data indicating when keys are pressed and released is returned.
In C, the libevdev library provides a wrapper around those. In python, you could use the python-evdev library. It should also be possible to read directly from the input device (though you may need to carefully read the kernel documentation & source to handle that properly).

I think that your problem is that multimedia keys do not map to terminal input.
It's possible that you could make progress by running xev to trap the key and xmodmap to map the key to a different input.
Alternatively, use something like TKinter and see if a graphical program doesn't collect the keypresses.
from Tkinter import *
root = Tk()
def key(event):
print "pressed", repr(event.char)
def callback(event):
frame.focus_set()
frame = Frame(root, width=100, height=100)
frame.bind("<Key>", key)
frame.bind("<Button-1>", callback)
frame.pack()
root.mainloop()
Another possibility is to map to an F key instead of a multimedia key. (i.e. F9)
Edit: Further research into this resulted in these two links:
Extra Keyboard Keys
Extra Keyboard Keys in Console
The console itself does not support multimedia keys. But it does support custom F keys. F30-F246 are always free. Rather than map to XF86Launch1, map to F70. Then map F70 to keyboard input in your keymap, or use the Python script you already wrote to handle it.

pycopia may be an option. I am using it with this bluetooth button and it seems to work fairly well. I am still working on getting it to reconnect to the button when the button goes to sleep and then comes back. Here's part of the script that I'm using:
keyboard.py:
from pycopia.OS.Linux import Input
from pycopia.OS.Linux import event
class Satechi(Input.EventDevice):
DEVNAME = 'Satechi'
def register_callback(self, cb):
self._callback = cb
def poll(self):
while 1:
ev = self.read()
if ev.evtype == event.EV_KEY:
self._callback(ev)
read_handler = poll
button.py
from keyboard import Satechi
def callback(event):
pass #Do something fun
if __name__ == '__main__':
pm = Satechi()
pm.find()
pm.register_callback(callback)
while 1:
try:
pm.poll()
except OSError:
pm = Satechi()
while True:
try:
pm.find()
pm.register_callback(callback)
break
except IOError:
pass
pm.close()
Where DEVNAME is the devices name in /proc/bus/input/devices.
You can print event in the callback to figure out what the code and value is for the button you are looking for

Try to read xinput test <id> stdout in a loop and catch the events you need.
Here is some example in Bash:
#!/bin/bash
keyboard_id=9 # use xinput to find your keyboard id
xinput test $keyboard_id | while read line ; do
case $line in
"key press 44") echo -e "\n == j pressed ==" ;;
"key press 45") echo -e "\n == k pressed ==" ;;
esac
done

Simplest method to call a function from keypress in python(3)

I have a python application in which a function runs in a recursive loop and prints updated info to the terminal with each cycle around the loop, all is good until I try to stop this recursion.
It does not stop until the terminal window is closed or the application is killed (control-c is pressed) however I am not satisfied with that method.
I have a function which will stop the loop and exit the program it just never has a chance to get called in the loop, so I wish to assign it to a key so that when it is pressed it will be called.
What is the simplest method to assign one function to one or many keys?

You can intercept the ctrl+c signal and call your own function at that time rather than
exiting.
import signal
import sys
def exit_func(signal, frame):
'''Exit function to be called when the user presses ctrl+c.
Replace this with whatever you want to do to break out of the loop.
'''
print("Exiting")
sys.exit(0) # remove this if you do not want to exit here
# register your exit function to handle the ctrl+c signal
signal.signal(signal.SIGINT, exit_func)
#loop forever
while True:
...
You should replace sys.exit(0) with something more useful to you. You could raise an exception and that except on it outside the loop body (or just finally) to perform your cleanup actions.

import keyboard
import sys
from time import sleep
def kb():
while True:
if keyboard.is_pressed("a"):
print("A key was pressed")
sys.exit(0)
def main():
kb()
if __name__ == "__main__":
main()

Here is some code
import keyboard
import sys
def kb():
while True:
#your code here
if keyboard.is_pressed("a"): #replace with your key
print("Key interrupt detected")
#cleanup here
sys.exit()
#or here
if __name__ == "__main__":
kb()
This program checks if you have pressed the key "A" every cycle. If you have, it exits.

import keyboard
def mywait():
keyboard.read_key()
def my_function():
print("hello")
def my_exit():
quit()
keyboard.add_hotkey('h', my_function)
keyboard.add_hotkey('esc', my_exit)
while True:
mywait()