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Transitioning from the conda or mamba to pixi#

Welcome to the guide designed to ease your transition from conda or mamba to pixi. This document compares key commands and concepts between these tools, highlighting pixi's unique approach to managing environments and packages. With pixi, you'll experience a project-based workflow, enhancing your development process, and allowing for easy sharing of your work.

Why Pixi?#

Pixi builds upon the foundation of the conda ecosystem, introducing a project-centric approach rather than focusing solely on environments. This shift towards projects offers a more organized and efficient way to manage dependencies and run code, tailored to modern development practices.

Key Differences at a Glance#

Task Conda/Mamba Pixi
Installation Requires an installer Download and add to path (See installation)
Creating an Environment conda create -n myenv -c conda-forge python=3.8 pixi init myenv followed by pixi add python=3.8
Activating an Environment conda activate myenv pixi shell within the project directory
Deactivating an Environment conda deactivate exit from the pixi shell
Running a Task conda run -n myenv python my_program.py pixi run python my_program.py (See run)
Installing a Package conda install numpy pixi add numpy
Uninstalling a Package conda remove numpy pixi remove numpy

No base environment

Conda has a base environment, which is the default environment when you start a new shell. Pixi does not have a base environment. And requires you to install the tools you need in the project or globally. Using pixi global install bat will install bat in a global environment, which is not the same as the base environment in conda.

Activating pixi environment in the current shell

For some advanced use-cases, you can activate the environment in the current shell. This uses the pixi shell-hook which prints the activation script, which can be used to activate the environment in the current shell without pixi itself. 

~/myenv > eval "$(pixi shell-hook)"

Environment vs Project#

Conda and mamba focus on managing environments, while pixi emphasizes projects. In pixi, a project is a folder containing a manifest(pixi.toml/pyproject.toml) file that describes the project, a pixi.lock lock-file that describes the exact dependencies, and a .pixi folder that contains the environment.

This project-centric approach allows for easy sharing and collaboration, as the project folder contains all the necessary information to recreate the environment. It manages more than one environment for more than one platform in a single project, and allows for easy switching between them. (See multiple environments)

Global environments#

conda installs all environments in one global location. When this is important to you for filesystem reasons, you can use the detached-environments feature of pixi. 

pixi config set detached-environments true
# or a specific location
pixi config set detached-environments /path/to/envs
This doesn't allow you to activate the environments using pixi shell -n but it will make the installation of the environments go to the same folder.

pixi does have the pixi global command to install tools on your machine. (See global) This is not a replacement for conda but works the same as pipx and condax. It creates a single isolated environment for the given requirement and installs the binaries into the global path. 

pixi global install bat
bat pixi.toml

Never install pip with pixi global

Installations with pixi global get their own isolated environment. Installing pip with pixi global will create a new isolated environment with its own pip binary. Using that pip binary will install packages in the pip environment, making it unreachable form anywhere as you can't activate it.

Automated switching#

With pixi you can import environment.yml files into a pixi project. (See import) 

pixi init --import environment.yml
This will create a new project with the dependencies from the environment.yml file.

Troubleshooting#

Encountering issues? Here are solutions to some common problems when being used to the conda workflow:

  • Dependency is excluded because due to strict channel priority not using this option from: 'https://conda.anaconda.org/conda-forge/' This error occurs when the package is in multiple channels. pixi uses a strict channel priority. See channel priority for more information.
  • pixi global install pip, pip doesn't work. pip is installed in the global isolated environment. Use pixi add pip in a project to install pip in the project environment and use that project.
  • pixi global install <Any Library> -> import <Any Library> -> ModuleNotFoundError: No module named '<Any Library>' The library is installed in the global isolated environment. Use pixi add <Any Library> in a project to install the library in the project environment and use that project.