How to request confirmation on program exit?

Question

I want to request a plaintext password when the user tries to close the script.

This is my code so far, the unrelated parts are hidden.

import signal
from time import sleep

_password = "iAmAdmin"


def _close(args):
    """Close the application."""
    if input("Preparing to close application.\n"
             "Please provide authentication password: ") == _password:
        print("Password correct. Application closing.")
        exit()
    else:
        print("Invalid password. Program will continue in 5 seconds.")
        sleep(5)


# Signal handler.
def sighandler(sig, frame):
    _close(None)


# Initiate the interface.
if __name__ == "__main__":
    signal.signal(signal.SIGINT, sighandler)
    clear()  # Function to clear the terminal.
    start()  # Display beginning help message.
    loop()  # An infinite loop requesting input and running functions.

When this script is run, and CTRL+C is pressed, this is the result:

Traceback (most recent call last):
  File "interface.py", line 96, in <module>
Preparing to close application.
Please provide authentication password:

And if SIGINT is sent again during this it closes silently. It should be ignored until the user inputs the correct password.

If the user does type the correct password, the application crashes:

Traceback (most recent call last):
  File "interface.py", line 96, in <module>
Preparing to close application.
Please provide authentication password: password
Invalid password. Program will continue in 5 seconds.
    loop()
  File "interface.py", line 67, in loop
    cmd = input(_prompt)
EOFError

Clearly there's something I'm missing. What is it?

Edit: By request, here is the code in the loop() function (contains line 67).

# All interface functionality below.
def loop():
    """Infinite loop that handles all interface commands."""
    while True:
        cmd = input(_prompt)  # Line 67.
        cmd, args = cmd.lower().split(" ", 1) if " " in cmd else (cmd, None)

        if cmd == "help":
            _help(cmds, args)
        elif cmd in cmds:
            cmds[cmd](args)
        else:
            print("Unrecognized command:", cmd, "\nType \"help\" for a list of commands.")

            suggestions = _suggest(cmds, cmd)

            if suggestions:
                print("\nDid you mean \"" + suggestions[0] + "\"?")

                if len(suggestions) > 1:
                    print("Similar commands:", ", ".join(suggestions[-1:]))

What does the file interface.py in line 67 contain? There's nothing wrong with the code you have shared. You may need to recheck the rest of the code — zeeks, Nov 18 '17 at 21:29
Rather than using a signal handler, I would try `try ... except KeyboardInterrupt:`. — xaav, Nov 18 '17 at 22:03
@xaav Where would you put that? It could go anywhere. It also wouldn't solve the problem of the user pressing the buttons twice. — Jacob Birkett, Nov 18 '17 at 22:04
@zeeks I have added the code to the question. See the edit I added. — Jacob Birkett, Nov 18 '17 at 22:05

xaav · Accepted Answer · 2017-11-19T00:39:36.640

1

from getpass import getpass
from time import sleep
from os import system, name as os_name


def clear():
    system("cls") if os_name == "nt" else system("clear")


def close():
    try:
        clear()
        password = getpass("Please provide authentication password to close the application.")
        if password == "admin":
            print("Password correct. Closing application now.\n")
            exit()
        else:
            print("Password incorrect. Application continues in 5 seconds.")
            sleep(5)
    except (KeyboardInterrupt, EOFError):
        close()


def loop():
    while True:
        cmd = input("> ")
        if cmd == "close":
            close()
        else:
            print("Hello World!")


def main():
    clear()
    try:
        loop()
    except (KeyboardInterrupt, EOFError):
        close()
        main()


if __name__ == "__main__":
    main()

edited Nov 19 '17 at 00:39

answered Nov 18 '17 at 22:10

xaav

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It doesn't. It just exits with a blank traceback. – Jacob Birkett Nov 18 '17 at 22:19
I checked it in IPython and it seemed to work as advertised. Note that the `guts` and `verifyPassword` functions actually need to do something for this to work. – xaav Nov 18 '17 at 22:29
Are you saying that i need to call `guts()` in `_verifyPassword()`? – Jacob Birkett Nov 18 '17 at 22:30
If the password is not verified, then yes. Also, you could start `guts` in another thread if you don't want it to stop while the password is being verified. – xaav Nov 18 '17 at 22:34
Here is my adaptation of the code you gave me. Everything works, except when I press `CTRL+C` when the prompt (`> `) is showing. https://pastebin.com/shjR3tj9 And here is the traceback https://pastebin.com/rHrcWqjG – Jacob Birkett Nov 18 '17 at 23:56
I sent you a link to the traceback, so no. – Jacob Birkett Nov 19 '17 at 00:52
I updated the answer after you posted that traceback. – xaav Nov 19 '17 at 01:05
That should work, should have thought of that. But why does it happen? – Jacob Birkett Nov 19 '17 at 01:06

How to request confirmation on program exit?

1 Answers1