Warn when `venv` target directory already contains an environment

[abdallhfattah]

Feature or enhancement

Proposal:

When a user runs:

python -m venv myenv

and the directory already contains a virtual environment, Python silently performs no action. This behavior can be confusing, as the user receives no indication that the command had no effect.

I propose that venv should display a simple warning when it detects an existing virtual environment so the user knows the operation didn’t make any changes.

Example of the suggested output:

$ python -m venv myenv
Existing virtual environment found at 'myenv'.
No changes were made.
Use '--clear' to recreate this environment.

This provides clarity while keeping behavior backward-compatible. Users who want to recreate the environment can explicitly use --clear.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

[FFY00]

That's not quite correct. Running the command on a directory already containing a venv will re-create it, though without clearing it.

In practice, this means if the Python version is the same, it won't basically do anything, but if it is different, it will update it.

$ python3.10 -m venv venv
$ cat venv/pyvenv.cfg
home = /usr/bin
include-system-site-packages = false
version = 3.10.14
$ python3.13 -m venv venv
$ cat venv/pyvenv.cfg
home = /usr/local/bin
include-system-site-packages = false
version = 3.13.0
executable = /usr/local/bin/python3.13
command = /usr/local/bin/python3.13 -m venv /home/anubis/test/overwrite-venv/venv

This isn't great either because on POSIX you will lose whatever was installed there — well, not completely, they will still be there, just in the site-packages directory for the old version. On Windows, from what I can tell, you will upgrade the environment, but will keep the packages from the previous version, which may be incompatible. None of this is great.

Related issues:

• Warn when running in a virtual environment that was created for a different minor Python version #127727
• Issue warning when running an outdated virtual environment after updating Python in-place #122099