[python] Stopping python using ctrl+c

I have a python script that uses threads and makes lots of HTTP requests. I think what's happening is that while a HTTP request (using urllib2) is reading, it's blocking and not responding to CtrlC to stop the program. Is there any way around this?

On Mac press Ctrl+\ to quit a python process attached to a terminal.

For the record, what killed the process on my Raspberry 3B+ (running raspbian) was Ctrl+'. On my French AZERTY keyboard, the touch ' is also number 4.

On a mac / in Terminal:

1. Show Inspector (right click within the terminal window or Shell >Show Inspector)
2. click the Settings icon above "running processes"
3. choose from the list of options under "Signal Process Group" (Kill, terminate, interrupt, etc).

Ctrl+D Difference for Windows and Linux

It turns out that as of Python 3.6, the Python interpreter handles Ctrl+C differently for Linux and Windows. For Linux, Ctrl+C would work mostly as expected however on Windows Ctrl+C mostly doesn't work especially if Python is running blocking call such as thread.join or waiting on web response. It does work for time.sleep, however. Here's the nice explanation of what is going on in Python interpreter. Note that Ctrl+C generates SIGINT.

Solution 1: Use Ctrl+Break or Equivalent

Use below keyboard shortcuts in terminal/console window which will generate SIGBREAK at lower level in OS and terminate the Python interpreter.

Mac OS and Linux

Ctrl+Shift+</kbd> or Ctrl+</kbd>

Windows:

• General: Ctrl+Break
• Dell: Ctrl+Fn+F6 or Ctrl+Fn+S
• Lenovo: Ctrl+Fn+F11 or Ctrl+Fn+B
• HP: Ctrl+Fn+Shift
• Samsung: Fn+Esc

Solution 2: Use Windows API

Below are handy functions which will detect Windows and install custom handler for Ctrl+C in console:

#win_ctrl_c.py

import sys

def handler(a,b=None):
    sys.exit(1)
def install_handler():
    if sys.platform == "win32":
        import win32api
        win32api.SetConsoleCtrlHandler(handler, True)

You can use above like this:

import threading
import time
import win_ctrl_c

# do something that will block
def work():
    time.sleep(10000)        
t = threading.Thread(target=work)
t.daemon = True
t.start()

#install handler
install_handler()

# now block
t.join()

#Ctrl+C works now!

Solution 3: Polling method

I don't prefer or recommend this method because it unnecessarily consumes processor and power negatively impacting the performance.

    import threading
    import time

    def work():
        time.sleep(10000)        
    t = threading.Thread(target=work)
    t.daemon = True
    t.start()
    while(True):
        t.join(0.1) #100ms ~ typical human response
    # you will get KeyboardIntrupt exception

You can open your task manager (ctrl + alt + delete, then go to task manager) and look through it for python and the server is called (for the example) _go_app (naming convention is: _language_app).

If I end the _go_app task it'll end the server, so going there in the browser will say it "unexpectedly ended", I also use git bash, and when I start a server, I cannot break out of the server in bash's shell with ctrl + c or ctrl + pause, but once you end the python task (the one using 63.7 mb) it'll break out of the server script in bash, and allow me to use the git bash shell.

Pressing Ctrl + c while a python program is running will cause python to raise a KeyboardInterrupt exception. It's likely that a program that makes lots of HTTP requests will have lots of exception handling code. If the except part of the try-except block doesn't specify which exceptions it should catch, it will catch all exceptions including the KeyboardInterrupt that you just caused. A properly coded python program will make use of the python exception hierarchy and only catch exceptions that are derived from Exception.

#This is the wrong way to do things
try:
  #Some stuff might raise an IO exception
except:
  #Code that ignores errors

#This is the right way to do things
try:
  #Some stuff might raise an IO exception
except Exception:
  #This won't catch KeyboardInterrupt

If you can't change the code (or need to kill the program so that your changes will take effect) then you can try pressing Ctrl + c rapidly. The first of the KeyboardInterrupt exceptions will knock your program out of the try block and hopefully one of the later KeyboardInterrupt exceptions will be raised when the program is outside of a try block.

• Forcing the program to close using Alt+F4 (shuts down current program)
• Spamming the X button on CMD for e.x.
• Taskmanager (first Windows+R and then "taskmgr") and then end the task.

Those may help.

The interrupt process is hardware and OS dependent. So you will have very different behavior depending on where you run your python script. For example, on Windows machines we have Ctrl+C (SIGINT) and Ctrl+Break (SIGBREAK).

So while SIGINT is present on all systems and can be handled and caught, the SIGBREAK signal is Windows specific (and can be disabled in CONFIG.SYS) and is really handled by the BIOS as an interrupt vector INT 1Bh, which is why this key is much more powerful than any other. So if you're using some *nix flavored OS, you will get different results depending on the implementation, since that signal is not present there, but others are. In Linux you can check what signals are available to you by:

$ kill -l
 1) SIGHUP       2) SIGINT       3) SIGQUIT      4) SIGILL       5) SIGTRAP
 6) SIGABRT      7) SIGEMT       8) SIGFPE       9) SIGKILL     10) SIGBUS
11) SIGSEGV     12) SIGSYS      13) SIGPIPE     14) SIGALRM     15) SIGTERM
16) SIGURG      17) SIGSTOP     18) SIGTSTP     19) SIGCONT     20) SIGCHLD
21) SIGTTIN     22) SIGTTOU     23) SIGIO       24) SIGXCPU     25) SIGXFSZ
26) SIGVTALRM   27) SIGPROF     28) SIGWINCH    29) SIGPWR      30) SIGUSR1
31) SIGUSR2     32) SIGRTMAX

So if you want to catch the CTRL+BREAK signal on a linux system you'll have to check to what POSIX signal they have mapped that key. Popular mappings are:

CTRL+\     = SIGQUIT 
CTRL+D     = SIGQUIT
CTRL+C     = SIGINT
CTRL+Z     = SIGTSTOP 
CTRL+BREAK = SIGKILL or SIGTERM or SIGSTOP

In fact, many more functions are available under Linux, where the SysRq (System Request) key can take on a life of its own...

Capture the KeyboardInterrupt (which is launched by pressing ctrl+c) and force the exit:

from sys import exit

try:
    # Your code
    command = input('Type your command: ')

except KeyboardInterrupt:
    # User interrupt the program with ctrl+c
    exit()

This post is old but I recently ran into the same problem of Ctrl+C not terminating Python scripts on Linux. I used Ctrl+\ (SIGQUIT).

If it is running in the Python shell use Ctrl + Z, otherwise locate the python process and kill it.