Why doesn't Python include non-blocking keyboard input function?

[Michael Torrie]

On 10/27/2016 04:07 AM, Terry Reedy wrote:
> As I and others have said, those keyboard functions are not available on 
> text terminals.  I predict that keyboard functions that so not work on 
> all systems will never become built-ins.  But some are available with an 
> import.

Sure you can't get a keyboard scancode when you're in terminal. But you
can get "keystrokes" as it were, without having to read an entire line
from standard in.  I use editors and programs all the time which are
interactive (they don't buffer keyboard input into lines) in the
terminal.  vim, nano, pico, mc, etc.

Is this not what BartC is talking about?  A way of reading in
"keystrokes" in a terminal.  Whether this is coming from a canned file
via a pipe or a real keyboard and screen attached to a TTY doesn't
really matter.  There are implementations of curses for the Windows
console, but I doubt they are supported by the python curses module.
But at least curses provides a means of doing this for programmers in a
unix environment.

For mostly nostalgic reasons I play around with the FreeBASIC compiler
and it tries to faithfully emulate the old key input that BASICs of yore
did. Such as inkey$ (which returns nothing if no keystroke is
available).  It runs more or less as advertised in a terminal window on
Linux, or the console on Windows. They even go so far as to emulate the
old MS-DOS keycodes for things like arrow keys so that old code can
still run faithfully.  I think this is the sort of thing BartC would
like to see in Python.  It's certainly possible, even on terminals, but
unlikely to happen for reasons that have been well-stated already by others.

> Python optionally comes with a sophisticated keyboard api.  The PSF 
> (python.org) CPython builds for Windows and Mac include that API.  On 
> Windows, so is the required tcl/tk build.  The premise of the subject 
> line, that Python does not include 'non-blocking keyboard input 
> functions', is not true.

I would think curses would provide the needed functionality without
tkinter or an X server.  It's limited in that only key combinations that
have control code representation can be detected, but you can definitely
use arrow keys, function keys, etc.  And I've seen curses interactive
games so I know they can be read without blocking the whole program.