New REPL on Windows swallows characters entered via AltGr

[chris-eibl]

Bug report

Bug description:

E.g. on my keyboard with German layout, { is usually entered via pressing the AltGr key and 7, i.e. AltGr+7.

Likewise, }, [, ], \ and some more can only be entered via AltGr.

But since #128388 / #128389 these are swallowed by the REPL on Windows and can no longer be entered.

On 3.13.3, this happens independent from the terminal mode.

On main, this only happens in legacy Windows terminals, where the virtual terminal mode is turned off (e.g. cmd.exe).

In virtual terminal mode there are other issues, see #131878.

Many other keyboard layouts like French, Czech, etc, use the AltGr key, too, and suffer the same bug (tested changing my keyboard layout).

CPython versions tested on:

3.14, 3.13

Operating systems tested on:

Windows

Linked PRs

• GH-132439: REPL on Windows swallows characters entered via AltGr #132440

[picnixz]

@chris-eibl Small tip (and welcome to you as a triager!): we keep the "needs backport" labels for PRs and reserve version labels to issues so to indicate which Python versions are affected (and I personally leave out version labels if every Python version is affected, unless it's a security issue).

[chris-eibl]

Yeah, I was unsure about the "needs backport" for issues myself.

Regarding the "versions affected": this only applies to 3.13 and 3.14, because only those two feature the new REPL - hence we maybe should keep them in this case on the issue?

[picnixz]

Yes, we can keep them as it's really 3.13 and 3.14 specific. In general, once a version becomes EOL or security-only, we also remove or update the labels (technically, we could even remove them as 3.12 is now security-only so those issues won't necessarily be fixed)

[noisefloor]

I can confirm this bug, tested on two different Windows 11 machines. Characters accessible via ALT GR on a German keyboard, most notably for programming Python { [ ] } , work randomly (square brackets) or not at all (curly brackets). Tested with Python 3.13.3 installed from the Microsoft Store. For Python 3.12.10 installed from the Microsoft Store, all keys / characters work just fine.

[mettvterritory]

I've encountered this as well.
Bad Workaround: If you first press AltGR + 8, you can then enter exactly one AltGr grapheme.
So,
AltGR + 8, AltGr + 7 produces '{' on a German keyboard.
AltGR + 8, AltGr + Q produces '@' on a German keyboard.

[chris-eibl]

For me, the issue only occurs in an "old terminal", e.g. using cmd.exe. In a Windows terminal (e.g. powershell), the new REPL runs in virtual terminal mode

cpython/Lib/_pyrepl/windows_console.py

Lines 115 to 118 in 45c447b

	def _supports_vt():
	try:
	import nt
	return nt._supports_virtual_terminal()

where I can use AltGr as usual.

But the "virtual terminal mode" has other problems (#131878): I can no longer enter äÄöÖüÜ, etc., which work in the "old terminal", though.

[john-hen]

For me, the issue only occurs in an "old terminal", e.g. using cmd.exe. In a Windows terminal (e.g. powershell), the new REPL runs in virtual terminal mode

I think that's only true for the 3.14 developer preview. In the Python 3.13.3 release, there is no _supports_vt() function in windows_console.py. I have this issue no matter the terminal (the old Command Prompt and the new Windows Terminal) nor the shell (cmd.exe and PowerShell).

I went so far as to hot-patching windows_console.py locally. The REPL as of 3.13.3 is unusable for me otherwise., You don't get very far in Python without curly braces or square brackets. This is not supposed to happen in a bug-fix release.

[chris-eibl]

Ups, yeah, was imprecise on this one: can confirm that 3.13 is broken in the old and the new console.

[NSK-Guru]

This also occurs on danish keyboards (on win10). Can't input chars: @£${[]}|€~
Fallback to 3.13.2 worked for me.

[chris-eibl]

You can also turn off the new REPL if you do not want to fallback on an earlier version:
https://docs.python.org/3/using/cmdline.html#envvar-PYTHON_BASIC_REPL