Double parenthesis in activated venv generated by Python 3.12.10

[IterableTrucks]

Bug report

Bug description:

python3.12 -m venv venv
source venv/bin/activate

There will be double parenthesis displayed on the terminal. This bug may be related to this commit because Python 3.12.9 is normal.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[hugovk]

Please could you paste the terminal output?

This is what I get on macOS using iTerm:

/private/tmp via  v3.1.3
❯ python3.12 -m venv venv
source venv/bin/activate

/private/tmp via  v3.12.10 (venv) via  v3.1.3 took 10s
❯ python3.12 --version
Python 3.12.10

/private/tmp via  v3.12.10 (venv) via  v3.1.3

[i9wa4]

I encountered this too.

[srv1] [2025-04-10 22:27:08] zsh [~]
$ lsb_release -d
No LSB modules are available.
Description:    Ubuntu 24.04.2 LTS
[srv1] [2025-04-10 22:27:26] zsh [~]
$ pyenv global 3.12.10
[srv1] [2025-04-10 22:27:27] zsh [~]
$ which python
/home/i9wa4/.pyenv/shims/python
[srv1] [2025-04-10 22:27:35] zsh [~]
$ python --version
Python 3.12.10
[srv1] [2025-04-10 22:27:58] zsh [~]
$ python -m venv venv3.12.10
[srv1] [2025-04-10 22:28:11] zsh [~]
$ source venv3.12.10/bin/activate
((venv3.12.10) ) [srv1] [2025-04-10 22:28:11] zsh [~]
$ 

[brianschubert]

I can reproduce this. I think this may be related to this diff, which was included in the 3.12 backport, but not in the main PR

 if [ -z "${VIRTUAL_ENV_DISABLE_PROMPT:-}" ] ; then
     _OLD_VIRTUAL_PS1="${PS1:-}"
-    PS1=__VENV_PROMPT__"${PS1:-}"
+    PS1="("__VENV_PROMPT__") ${PS1:-}"
     export PS1
-    VIRTUAL_ENV_PROMPT=__VENV_PROMPT__
-    export VIRTUAL_ENV_PROMPT
 fi

For context, the generated activate script looks like this:

# [...]
VIRTUAL_ENV_PROMPT='(venv) '
export VIRTUAL_ENV_PROMPT

# unset PYTHONHOME if set
# this will fail if PYTHONHOME is set to the empty string (which is bad anyway)
# could use `if (set -u; : $PYTHONHOME) ;` in bash
if [ -n "${PYTHONHOME:-}" ] ; then
    _OLD_VIRTUAL_PYTHONHOME="${PYTHONHOME:-}"
    unset PYTHONHOME
fi                                                                                                                                                   

if [ -z "${VIRTUAL_ENV_DISABLE_PROMPT:-}" ] ; then
    _OLD_VIRTUAL_PS1="${PS1:-}"
    PS1="("'(venv) '") ${PS1:-}"
    export PS1 
fi
# [...]

cc @vsajip

[StanFromIreland]

This issue should be closed, it only affects 3.12 which no longer allows bugfixes.

[hugovk]

Reproducible in 3.12:

❯ docker run --rm -it python:3.12 bash
root@9131fb969a1b:/# python3 --version
Python 3.12.10
root@9131fb969a1b:/# python -m venv venv
root@9131fb969a1b:/# source venv/bin/activate
((venv) ) root@9131fb969a1b:/#
exit

But not 3.13:

❯ docker run --rm -it python:3.13 bash
root@05795675a6a3:/# python3 --version
Python 3.13.3
root@05795675a6a3:/# python -m venv venv
root@05795675a6a3:/# source venv/bin/activate
(venv) root@05795675a6a3:/#
exit

[StanFromIreland]

Very unfortunate, introduced just days before the deadline, and very visible too :-(

[hugovk]

All the more reason to upgrade to Python 3.13, and get all the other bugfixes too 👍

[gernophil]

Came here pretty late. Is this only a cosmetic bug or does it have any consequences?

[hugovk]

Likely only cosmetic.

[DellAnderson]

In case anyone wants to fix it themselves in a fork, here's what I think is going on:

The venv activate script generated by Python includes a redundant wrapping of parentheses and a trailing space in the PS1 prompt assignment.

In current versions (3.11, 3.12, not sure about 3.13), eg when creating a ~/venv312 environment:

the generated activate script includes the following:

VIRTUAL_ENV_PROMPT='(venv312) ' # note parens & trailing space.
...
Line 57
PS1="("VENV_PROMPT") ${PS1:-}" # note additional parens & interval space

This results in a prompt like: "((venv312) ) usersprompt$" prompt with double parentheses and an extra trailing space.

apparently because the script adds more parens & spaces in line 70:

https://github.com/python/cpython/blob/main/Lib/venv/scripts/common/activate
line 57
VIRTUAL_ENV_PROMPT=VENV_PROMPT
...
line 70
PS1="("VENV_PROMPT") ${PS1:-}" # Note added parens & trailing space around VENV_PROMPT

Suggested Fix:

Suggest use either inject the environment name itself (e.g., venv312) into the prompt string,
and use only the shell script to format it, or if necessary (less optimal)
Use the VENV_ENV_PROMPT as is without adding additional parens & spaces

#https://github.com/python/cpython/blob/main/Lib/venv/scripts/common/activate
line 57
VIRTUAL_ENV_PROMPT="(VENV_NAME)" #use only venv name, not a preformatted prompt
...
line 70
PS1="${VIRTUAL_ENV_PROMPT} ${PS1:-}" #remove extra parens & space here if unable to use VENV_NAME

This avoids duplication and makes the script easier to read, maintain or override.

The change should apply to:

Lib/venv/scripts/common/activate

May also need to remove formatting from template injection code here:
https://github.com/python/cpython/blob/main/Lib/venv/__init__.py (where

line 483 def replace_variables(self, text, context):

line 496 'VENV_NAME': context.env_name,
line 497 'VENV_PROMPT': context.prompt,