Double parenthesis in activated venv generated by Python 3.12.10

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

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

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 [~]
$

@vsajip

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

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

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

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

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

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

Likely only cosmetic.

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,

I can confirm that 3.13.5 at least has fixed this bug. It's such a simple but annoying one it's too bad it won't be backported to 3.11 & 3.12. There was some mention in the 'blame' section about quotes for avoiding injection so perhaps there is a security risk?

Just a +1 to say this is what I'd call out-of-character for Python at this point in its life? Introducing a bug into the last bugfix release of a version is disappointing. To compliment sandwich it, I suppose it says a lot that Python has gotten to the maturity where we can expect that things like this won't happen. But then they do happen. I can see that this won't get fixed, but with 3.13 being effectively a major version bump (due to cython major version incompatibility) and needing long runway, this—admittedly cosmetic—unfixable bug isn't up to the standard of professionalism I've come to expect from the hardworking maintainers of Python. Keep working hard, and know that I still believe in you all now more than I ever did before!

We don't use SemVer and every Python feature release is effectively a "major" bump due to removed deprecations.

If you'd like to help out, we have 2k open PRs that can benefit from review. Also the last ever 3.9 release is going out any day now before its EOL, so you're welcome to double check already merged PRs to that branch.

Navigation Menu

Repository navigation

Double parenthesis in activated venv generated by Python 3.12.10 #132361

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Double parenthesis in activated venv generated by Python 3.12.10 #132361

Description

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Activity

hugovk commented on Apr 10, 2025

i9wa4 commented on Apr 10, 2025

brianschubert commented on Apr 10, 2025

StanFromIreland commented on Apr 15, 2025

hugovk commented on Apr 16, 2025

StanFromIreland commented on Apr 16, 2025

hugovk commented on Apr 16, 2025

gernophil commented on May 22, 2025

hugovk commented on May 22, 2025

DellAnderson commented on Jul 13, 2025

DellAnderson commented on Jul 14, 2025

cdjameson commented on Sep 19, 2025

hugovk commented on Sep 20, 2025

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions