Prevent a console app from closing when not invoked from an existing terminal?

Question

There are many variants on this kind of question. However I am specifically after a way to prevent a console application in Python from closing when it is not invoked from a

Answer 1

On Unix, sys.stdin.isatty() reliably tells you whether standard input is coming from a terminal-like device (or is otherwise redirected), and similarly for the same method on sys.stdout and sys.stderr -- so you can use those calls to determine whether the application is being executed interactively or in some non-interactive environment (such as a cron job). Exactly how you want to use them depends on what you want to do if (for example) both standard input and output are redirected to a non-terminal but standard error is going to a terminal -- consider each of the 8 possibilities, from all of them redirected to non-terminals to none of them, and decide what you want to do in each case.

On Windows the situation is different since executing a .py file (as opposed to a .pyw file) will create a new transient console (there's no exactly equivalent situation in Unix); I assume that's the case you want to deal with? (Or is it just about redirection of standard I/O streams to files, which is possible in Windows roughly just like in Unix?). I think the best approach in Windows might be to use win32api.SetConsoleCtrlHandler to set a handler for such events as CTRL_CLOSE_EVENT -- this way the handler should be invoked (in this case, when the console closes) if there is a console for the process, but not otherwise. Or, if all you care about is whether a console is there at all or not (and prefer to handle things your way otherwise), try calling win32api.GetConsoleTitle in the try leg of a try/except statement -- it will generate an exception (which you catch and respond to by setting a boolean variable of yours to False) if there's no console, and just work (in which case you set that boolean variable to True) if there is a console.