Pasting in new REPL is slow

[natedogith1]

Bug report

Bug description:

Pasting large blocks of text in the new REPL is slow. Tested by pasting the following string (3035 characters):

test value

"""1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"""

When using the old repl (started via $env:PYTHON_BASIC_REPL="true"; python in powershell), pasting the string is near immediate. When using the new repl (started via python in powershell), pasting the string takes 15 seconds.

The closed issue #119517 also mentioned some pasting performance issues, though that was for Linux with significantly more characters.

CPython versions tested on:

3.13

Operating systems tested on:

Windows

[StanFromIreland]

Possibly a windows issue, something to do with powershell? On linux (main branch build) it pastes as expected, instantly.

cc windows expert @zooba

[zooba]

It's no good looking at me, I know nothing about the new repl (other than that I've suggested a couple of times that it should stop using ctypes and use native code instead, which could be the cause of any performance issue).

@pablogsal @lysnikolaou @ambv are code owners for the REPL.

[natedogith1]

I also see this when python is started from the win-r run dialog.

Tested some other environments, using the first 604 lines of this copy of Frankenstein (32,003 characters) (same as #119517 did). WSL old REPL takes ~2 seconds. WSL new REPL takes ~4 seconds, Powershell old REPL takes ~1 second. Powershell new REPL takes ~55 seconds for just the first 25 lines to appear; when pasting only the first 25 lines (659 characters) it takes ~2 seconds.