Python Dependency Manager Companion

# Working with Virtual Environments When you run [`pdm init`](../reference/cli.md#init) command, PDM will [ask for the Python interpreter to use](./project.md#choose-a-python-interpreter) in the project, which is the base interpreter to install dependencies and run tasks. Compared to [PEP 582](https://www.python.org/dev/peps/pep-0582/), virtual environments are considered more mature and have better support in the Python ecosystem as well as IDEs. Therefore, virtualenv is the default mode if not configured otherwise. !!! note "Configure pdm to use virtual environment or PEP 582" By default pdm is configured to use virtual environment instead of PEP 582. But this behavior can be changed with `pdm config python.use_venv False` config variable. **Virtual environments will be used if the project interpreter (the interpreter stored in `.pdm-python`, which can be checked by `pdm info`) is from a virtualenv.** ## Virtualenv auto-creation By default, PDM prefers to use the virtualenv layout as other package managers do. When you run `pdm install` the first time on a new PDM-managed project, whose Python interpreter is not decided yet, PDM will create a virtualenv in `<project_root>/.venv`, and install dependencies into it. In the interactive session of `pdm init`, PDM will also ask to create a virtualenv for you. You can choose the backend used by PDM to create a virtualenv. Currently it supports three backends: - [`virtualenv`](https://virtualenv.pypa.io/)(default) - `venv` - `conda` You can change it by `pdm config venv.backend [virtualenv|venv|conda]`. +++ 2.13.0 Moreover, when `python.use_venv` config is set to `true`, PDM will always try to create a virtualenv when using `pdm use` to switch the Python interpreter. ## Create a virtualenv yourself You can create more than one virtualenvs with whatever Python version you want. ```bash # Create a virtualenv based on 3.9 interpreter pdm venv create 3.9 # Assign a different name other than the version string pdm venv create --name for-test 3.9 # Use venv as the backend to create, support 3 backends: virtualenv(default), venv, conda pdm venv create --with venv 3.10 ``` ## The location of virtualenvs If no `--name` is given, PDM will create the venv in `<project_root>/.venv`. Otherwise, virtualenvs go to the location specified by the `venv.location` configuration. They are named as `<project_name>-<path_hash>-<name_or_python_version>` to avoid name collision. You can disable the in-project virtualenv creation by `pdm config venv.in_project false`. And all virtualenvs will be created under `venv.location`. ## Reuse the virtualenv you created elsewhere You can tell PDM to use a virtualenv you created in preceding steps, with [`pdm use`](../reference/cli.md#use): ```bash pdm use -f /path/to/venv ``` ## Virtualenv auto-detection When no interpreter is stored in the project config or `PDM_IGNORE_SAVED_PYTHON` env var is set, PDM will try to detect possible virtualenvs to use: - `venv`, `env`, `.venv` directories in the project root - The currently activated virtualenv, unless `PDM_IGNORE_ACTIVE_VENV` is set ## List all virtualenvs created with this project ```bash $ pdm venv list Virtualenvs created with this project: - 3.8.6: C:\Users\Frost Ming\AppData\Local\pdm\pdm\venvs\test-project-8Sgn_62n-3.8.6 - for-test: C:\Users\Frost Ming\AppData\Local\pdm\pdm\venvs\test-project-8Sgn_62n-for-test - 3.9.1: C:\Users\Frost Ming\AppData\Local\pdm\pdm\venvs\test-project-8Sgn_62n-3.9.1 ``` ## Show the path or python interpreter of a virtualenv ```bash pdm venv --path for-test pdm venv --python for-test ``` ## Remove a virtualenv ```bash $ pdm venv remove for-test Virtualenvs created with this project: Will remove: C:\Users\Frost Ming\AppData\Local\pdm\pdm\venvs\test-project-8Sgn_62n-for-test, continue? [y/N]:y Removed C:\Users\Frost Ming\AppData\Local\pdm\pdm\venvs\test-project-8Sgn_62n-for-test ``` ## Activate a virtualenv Instead of spawning a subshell like what `pipenv` and `poetry` do, `pdm venv` doesn't create the shell for you but print the activate command to the console. In this way you won't leave the current shell. You can then feed the output to `eval` to activate the virtualenv: === "bash/csh/zsh" ```bash $ eval $(pdm venv activate for-test) (test-project-for-test) $ # Virtualenv entered ``` === "Fish" ```bash $ eval (pdm venv activate for-test) ``` === "Powershell" ```ps1 PS1> Invoke-Expression (pdm venv activate for-test) ``` Additionally, if the project interpreter is a venv Python, you can omit the name argument following activate. !!! note `venv activate` **does not** switch the Python interpreter used by the project. It only changes the shell by injecting the virtualenv paths to environment variables. For the aforementioned purpose, use the `pdm use` command. For more CLI usage, see the [`pdm venv`](../reference/cli.md#venv) documentation. !!! tip "Looking for `pdm shell`?" PDM doesn't provide a `shell` command because many fancy shell functions may not work perfectly in a subshell, which brings a maintenance burden to support all the corner cases. However, you can still gain the ability via the following ways: - Use `pdm run $SHELL`, this will spawn a subshell with the environment variables set properly. **The subshell can be quit with `exit` or `Ctrl+D`.** - Add a shell function to activate the virtualenv, here is an example of BASH function that also works on ZSH: ```bash pdm() { local command=$1 if [[ "$command" == "shell" ]]; then eval $(pdm venv activate) else command pdm $@ fi } ``` Copy and paste this function to your `~/.bashrc` file and restart your shell. For `fish` shell you can put the following into your `~/fish/config.fish` or in `~/.config/fish/config.fish` ```fish function pdm set cmd $argv[1] if test "$cmd" = "shell" eval (pdm venv activate) else command pdm $argv end end ``` Now you can run `pdm shell` to activate the virtualenv. **The virtualenv can be deactivated with `deactivate` command as usual.** ## Prompt customization By default when you activate a virtualenv, the prompt will show: `{project_name}-{python_version}`. For example if your project is named `test-project`: ```bash $ eval $(pdm venv activate for-test) (test-project-3.10) $ # {project_name} == test-project and {python_version} == 3.10 ``` The format can be customized before virtualenv creation with the [`venv.prompt`](../reference/configuration.md) configuration or `PDM_VENV_PROMPT` environment variable (before a `pdm init` or `pdm venv create`). Available variables are: - `project_name`: name of your project - `python_version`: version of Python (used by the virtualenv) ```bash $ PDM_VENV_PROMPT='{project_name}-py{python_version}' pdm venv create --name test-prompt $ eval $(pdm venv activate test-prompt) (test-project-py3.10) $ ``` ## Run a command in a virtual environment without activating it ```bash # Run a script pdm run --venv test test # Install packages pdm sync --venv test # List the packages installed pdm list --venv test ``` There are other commands supporting `--venv` flag or `PDM_IN_VENV` environment variable, see the [CLI reference](../reference/cli.md). You should create the virtualenv with `pdm venv create --name <name>` before using this feature. ## Switch to a virtualenv as the project environment By default, if you use `pdm use` and select a non-venv Python, the project will be switched to [PEP 582 mode](./pep582.md). We also allow you to switch to a named virtual environment via the `--venv` flag: ```bash # Switch to a virtualenv named test $ pdm use --venv test # Switch to the in-project venv located at $PROJECT_ROOT/.venv $ pdm use --venv in-project ``` ## Disable virtualenv mode You can disable the auto-creation and auto-detection for virtualenv by `pdm config python.use_venv false`. **If venv is disabled, PEP 582 mode will always be used even if the selected interpreter is from a virtualenv.** ## Including pip in your virtual environment By default PDM will not include `pip` in virtual environments. This increases isolation by ensuring that _only your dependencies_ are installed in the virtual environment. To install `pip` once (if for example you want to install arbitrary dependencies in CI) you can run: ```bash # Install pip in the virtual environment pdm run python -m ensurepip # Install arbitrary dependencies # These dependencies are not checked for conflicts against lockfile dependencies! pdm run python -m pip install coverage ``` Or you can create the virtual environment with `--with-pip`: ```bash pdm venv create --with-pip 3.9 ``` See the [ensurepip docs](https://docs.python.org/3/library/ensurepip.html) for more details on `ensurepip`. If you want to permanently configure PDM to include `pip` in virtual environments you can use the [`venv.with_pip`](../reference/configuration.md) configuration.