On 20Dec2020 15:48, Christopher Barker <[email protected]> wrote:
>On Sun, Dec 20, 2020 at 1:23 PM Cameron Simpson <[email protected]> wrote:
>> My anger at programmes which gratuitously clear the screen is large.
>
>There are a LOT of bad things one can do with Python, I don't think we need
>to make something difficult simply because it can be abused.
True.
>One problem is: what does it mean? On a terminal, easy. But in a GUI?
>> Clear the screen (possibly forbidden)? A window? The "main" window?
>> Etc.
>
>It would be meaningless outside of a terminal -- call it `clear_term` if
>you want.
+1
>> Anyway, I think it should be in curses (or be loaded via curses on
>> demand),
>
>That would be great, though I just looked at the 3.9 docs and saw:
>"The Windows version of Python doesn’t include the curses module."
Yeah, Windows.
>So we're pretty much back to square one.
No, for Windows we shell out to its command line unless a Windows person
knows what to do. We could hardwire the ANSI clear screen sequence as a
fallback when there's no curses module, that's easy with a try/import.
>I think the idea here is that we want a simple way, out of the box that
>people can use to clear the terminal, that will work on most commonly
>configured systems out of the box, and can be overridden (monkey patched)
>to work in IDEs (e.g. Idle), custom terminal emulators (e.g. iPython
>Qtconsole), etc. We don't want to require a full curses implementation.
Ok. I still think on UNIX we want curses as the preferred choice since
to accomodates all terminal types. But a fallback assuming ANSI seems
sensible to me, unless there's a Windows counter example.
Untested:
cls_bs = None
def clear_screen():
if cls_bs is None:
try:
import curses
except ImportError:
cls_bs=curses.tigetstr('clear')
print(cls_bs.encode(), end='', flush=True)
>I just tried that on my mac and tigetstr('cl') simply returns None with
>no effect.
Yeah. 'clear' works though.
>The tutorial seems to indicate there is a clear method available, so I
>did
>try that, and it does nothing on my Mac with the default terminal app:
>
>def clear_screen():
> from curses import wrapper
>
> def clr(stdscr):
> # Clear screen
> stdscr.clear()
> wrapper(clr)
>clear_screen()
Nonono.
That requires a full curses init, "full screen curses mode programme"
etc. We just want the terminal escape sequence. setupterm() inits the
terminal db access, then off we go. As above.
>>is it so bad to use a subprocess?
>>
>> Yes. It is _really slow_,
>
>could it possible be slow enough to matter? not the kind of thing that's in
>a tight loop.
In your imagined use case. Guarenteed one day this will be in a tight
loop. In a simulation or something.
>depends on external reaources which might not
>> be there,
>
>oh, like the curses lib ;-)
Hahaha. Batteries supplied.
Cheers,
Cameron Simpson <[email protected]>
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