What is PDM?
PDM is meant to be a next generation Python package management tool. It was originally built for personal use. If you feel you are going well with
Poetry and don’t want to introduce another package manager, just stick to it. But if you are missing something that is not present in those tools, you can probably find some goodness in
PEP 582 proposes a project structure as below:
foo __pypackages__ 3.8 lib bottle myscript.py
There is a
__pypackages__ directory in the project root to hold all dependent libraries, just like what
npm does. Read more about the specification here.
Highlights of features
- PEP 582 local package installer and runner, no virtualenv involved at all.
- Simple and relatively fast dependency resolver, mainly for large binary distributions.
- A PEP 517 build backend.
- A full-featured plug-in system.
- PEP 621 project metadata format.
Why not virtualenv?
The majority of Python packaging tools also act as virtualenv managers to gain the ability to isolate project environments. But things get tricky when it comes to nested venvs: One installs the virtualenv manager using a venv encapsulated Python, and create more venvs using the tool which is based on an encapsulated Python. One day a minor release of Python is released and one has to check all those venvs and upgrade them if required.
PEP 582, on the other hand, introduces a way to decouple the Python interpreter from project environments. It is a relative new proposal and there are not many tools supporting it (one that does is pyflow, but it is written with Rust and thus can’t get much help from the big Python community and for the same reason it can’t act as a PEP 517 backend).
PDM requires python version 3.7 or higher.
Like Pip, PDM provides an installation script that will install PDM into an isolated environment.
curl -sSL https://raw.githubusercontent.com/pdm-project/pdm/main/install-pdm.py | python -
(Invoke-WebRequest -Uri https://raw.githubusercontent.com/pdm-project/pdm/main/install-pdm.py -UseBasicParsing).Content | python -
The installer will install PDM into the user site and the location depends on the system:
You can pass additional options to the script to control how PDM is installed:
usage: install-pdm.py [-h] [-v VERSION] [--prerelease] [--remove] [-p PATH] [-d DEP] optional arguments: -h, --help show this help message and exit -v VERSION, --version VERSION | envvar: PDM_VERSION Specify the version to be installed, or HEAD to install from the main branch --prerelease | envvar: PDM_PRERELEASE Allow prereleases to be installed --remove | envvar: PDM_REMOVE Remove the PDM installation -p PATH, --path PATH | envvar: PDM_HOME Specify the location to install PDM -d DEP, --dep DEP | envvar: PDM_DEPS Specify additional dependencies, can be given multiple times
You can either pass the options after the script or set the env var value.
Alternative Installation Methods
If you are on MacOS and using
homebrew, install it by:
If you are on Windows and using Scoop, install it by:
PS> scoop install pdm
PS> scoop bucket add frostming https://github.com/frostming/scoop-frostming.git PS> scoop install pdm
Otherwise, it is recommended to install
pdm in an isolated environment with
Or you can install it under a user site:
Initialize a new PDM project
Answer the questions following the guide, and a PDM project with a
pyproject.toml file will be ready to use.
Install dependencies into the
You can add multiple dependencies in the same command. After a while, check the
pdm.lock file to see what is locked for each package.
Run your script with PEP 582 support
Suppose you have a script
app.py placed next to the
__pypackages__ directory with the following content(taken from Flask’s website):
from flask import Flask app = Flask(__name__) @app.route('/') def hello_world(): return 'Hello World!' if __name__ == '__main__': app.run()
If you are a Bash user, set the environment variable by
eval "$(pdm --pep582)". Now you can run the app directly with your familiar Python interpreter:
$ python /home/frostming/workspace/flask_app/app.py * Serving Flask app "app" (lazy loading) ... * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
Ta-da! You are running an app with its dependencies installed in an isolated place, while no virtualenv is involved.
For Windows users, please refer to the doc about how to make it work.
If you are curious about how this works, check this doc section for some explanation.
$ docker pull frostming/pdm
Tell people you are using PDM in your project by including the markdown code in README.md:
Awesome PDM is a curated list of awesome PDM plugins and resources.
1. What is put in
PEP 582 is a draft proposal which still needs a lot of polishing. For instance, it doesn’t mention how to manage CLI executables. PDM makes the decision to put
include together with
2. How do I run CLI scripts in the local package directory?
The recommended way is to prefix your command with
pdm run. It is also possible to run CLI scripts directly from the outside. PDM’s installer has already injected the package path to the
sys.path in the entry script file.
3. What site-packages will be loaded when using PDM?
Packages in the local
__pypackages__ directory will be loaded before the system-level
site-packages for isolation.
4. Can I relocate or move the
__pypackages__ folder for deployment?
You’d better not. The packages installed inside
__pypackages__ are OS dependent. Instead, you should keep
pdm.lock in VCS and do
pdm sync on the target environment to deploy.
5. Can I use
pdm to manage a Python 2.7 project?
pdm itself can be installed under Python 3.7+ only, but it doesn’t restrict the Python used by the project.
This project is open sourced under MIT license, see the LICENSE file for more details.