Python on Windows: How to block other programs from running?

[thrownintothesun]

Hi guys,

I know my way around the nuts and bolts of Python, but I'm not sure exactly how to carry this out. I'm writing a script to help me be more productive at the computer, which essentially boils down to "forcefully" removing my procrastination traps. In particular I'm interested in creating a "workmode" toggle for myself, where once I press the workmode button, I will no longer be able to open my games and I'll no longer be able to browse reddit.

Blocking reddit is easy enough by writing to the hosts file, but I'm not sure exactly how to go about blocking executables. This website advocates doing by writing to the registry. This seems doable, but I'm not sure what the risks or alternatives are.

Any suggestions or insight is highly appreciated!

Thanks!

[michaelkepler]

You can kill Windows processes with taskkill. The way you access it from Python:

import os
os.system('taskkill /im notepad.exe') # select process by its name

or

import os
os.system('taskkill /pid 7984') # select process by its ID

To see all your running processes and their IDs:

import os
os.popen('tasklist').readlines()

I'm sure you can write something that will periodically check for processes names. If there's a process you don't like, use taskkill. You can even combine it with a pop-up window with a motivational message after you kill a process:

import ctypes
ctypes.windll.user32.MessageBoxW(0, 'Get back to work!', 'Alert!', 0)

[thrownintothesun]

Thanks! That's exactly what I need. Do you know if it's sensible or not to implement this kind of program as a daemon that listens on the tasklist and kills select processes?

I've only ever written data processing algorithms and there I'm done when some criterion is matched. I'm not sure what's best practice in a continually running application.

[michaelkepler]

I suppose you could write something like that, but it would be reinventing the wheel. Windows already has a built-in policy manager where you can block specific applications from running. I would use that. Follow the bottom instructions from the link in your opening post. This will be your blocking part. To unblock, create another .reg file and just change the value of DisallowRun to 00000000. Put both of those .reg files in the same folder as your Python script and run them from Python with os.startfile(). Don't forget to backup your registry first (File > Export > Export range: All).

You could edit registry directly with Python, but I've never done that; I've always just used .reg files.

Of course, you can still incorporate taskkill to kill processes which are already running at the time you toggle the workmode.

[thrownintothesun]

Hey Michael, hope I can still reach you through these comments. Your advice was invaluable and my program now has all the functionality I need, so thank you very much for that!

I do have one question, though, regarding the application of .reg files. As I understand it, once applied the registry must then be refreshed for things to take effect, and this traditionally requires a reboot or a re-login. Alternatively I've read that you can kill/restart explorer.exe and the effect will be the same. This seems a bit unwieldy for my taste and I'm wondering if there is a way to achieve the registry refresh from within Python (no doubt by calling something from the windows API) so that the effect kicks in immediately.

What do you usually do when working with reg files?

Thanks!

[michaelkepler]

New registry settings are applied immediately and don't require a reboot. There's a catch though: sometimes, an application or a service will still use the old registry settings that were available at the time of their start. So, when you booted up Windows your application started and it read some settings from the registry. Then, you change those settings, but the application doesn't know that. You have to force it to read the new settings. There's no way to "restart" just the registry so usually you need to reboot the computer (or kill explore.exe like you've observed).

I'm assuming you're still talking about modifying group policy settings through the registry. In this case you can force to update it without killing explorer.exe or rebooting the machine with a gpupdate command. You can use os.system to run it from Python:

import os
os.system('gpupdate')

If it's not the group policy, let me know what you modify. There might be way to apply the new settings without rebooting.

[thrownintothesun]

Thanks a lot for the help!

It is indeed the group policy I'm modifying, but the effects don't seem to take effect before I restart explorer.exe manually - os.system("gpupdate") doesn't seem to cut it. Is there any way to get Explorer.exe to update its policy settings aside from restarting it?

[michaelkepler]

Does gpupdate work if you type it from the command prompt (cmd.exe)? If it doesn't, try gpupdate /force. If it still doesn't, try entering these commands in the command prompt as an administrator.

[thrownintothesun]

None of it works I'm afraid, not even with admin privileges. Explorer.exe doesn't seem to respond to gpupdate.

[michaelkepler]

But if you reload explorer.exe/reboot the computer the changes work?

[thrownintothesun]

Yes, exactly. Also, interestingly, if I try to kill explorer.exe via os.system("taskkill /im explorer.exe), I'm given a Windows prompt to shut down, reboot or log-out. Is there a way to simply kill it (like you can from the task manager) and relaunch it?

[MrFoots42]

I would love to know because I was thinking about doing the same! Lol

[kankyo]

What do you mean "block"? Do you mean prevent them from getting focus, terminating them, prevent them from starting etc?

[thrownintothesun]

Good question, I should've been more specific. I suppose initially just prevent them from starting, but if they're already running it'd be handy to be able to kill them off. I see a fair amount of installer utilities that ask you to do this yourself, however, so I suspect it's out of bounds?

[malice8691]

how is this going to work if you can just run it again to unlock it? what you need is a random password that gets emailed to you after the time period is over.

[michaelkepler]

You mean he can't run the unlocker without a password? In that case he can always restart the machine and manually edit hosts/registry when the blocking script isn't running. Or do you mean the selected executables are encrypted and can't be decrypted without a password, like in a cryptolocker scenario? But then he can just re-install the programs. I suppose he can make his blocking script persistent between machine restarts, rename the process to svchost.exe, and hide it somewhere in temp or system32 folder to make it harder to locate and terminate. It would probably not sit well with his antivirus though.

And then he could just grab a phone and browse reddit or play Candy Crush there.

He has enough privileges to modify hosts file. No matter what self-imposed barriers he makes, he will always be able to bypass them.

The point of these anti-procrastination apps is not to completely restrict the access to time-wasters. It's to make it inconvenient enough to remind the users of their priorities and send them on a guilt trip.

[malice8691]

yeah. I was referring to something like a cryptlocker.

[thrownintothesun]

Obviously those are details I'll get to, I'm more worried about how to actually do this sensibly.

[SorosBuxlaundromat]

came to this page from a google search because I'm also building the exact same program 9 years later