[Python-ideas] Suggestion: Clear screen command for the REPL

[eryk sun]

On Sat, Sep 17, 2016 at 11:11 AM, João Matos <jcrmatos at gmail.com> wrote:
>On 17-09-2016 12:07, Oleg Broytman wrote:
>>
>>     Pressing [Ctrl]+[L] works for me.
>
> Doesn't work on Windows.

Windows 10 added VT100 support to the console, so you can create a
little cls() function to clear the screen:

    cls = lambda: print('\x1b[1J', end='', flush=True)

VT100 support isn't enabled by default. However, cmd.exe always
enables this mode. So run doskey.exe via os.system to enable VT100
mode while setting a convenient "cls" alias:

    import os
    os.system(r'doskey /exename=python.exe cls=cls()')

This alias substitutes "cls()" for "cls" at the beginning of a line.
This saves you from having to type "()" all the time. The alias isn't
active for other programs; e.g. if you execute
subprocess.call('powershell'), then "cls" will be the PowerShell alias
for Clear-Host.

You can also use ctypes instead of os.system and doskey.exe:

    import ctypes
    kernel32 = ctypes.WinDLL('kernel32')
    hStdOut = kernel32.GetStdHandle(-11)

    # enable VT100 mode
    mode = (ctypes.c_uint * 1)()
    kernel32.GetConsoleMode(hStdOut, mode)
    kernel32.SetConsoleMode(hStdOut, mode[0] | 4)

    # define a cls() function and set a console alias
    cls = lambda: print('\x1b[1J', end='', flush=True)
    kernel32.AddConsoleAliasW('cls', 'cls()', 'python.exe')

For older versions of Windows you can use ANSICON or ConEmu, which use
DLL injection to extend the console API. Python's colorama and
pyreadline modules should also work for this.