environmentyml

environment.yml, often referred to in casual writing as environmentyml, is a YAML file used by the Conda package manager to declare and reproduce software environments. It captures the specific packages, their versions, and the channels from which they should be installed, enabling consistent environments across machines and collaborators. While Conda is the primary tool, similar declarative environment files exist in related ecosystems, but environment.yml remains the standard in Conda projects.

A typical environment.yml contains keys such as name, channels, and dependencies. The name assigns a label to the environment, channels specify package sources (for example conda-forge), and dependencies lists the packages to install. Dependencies can include exact version constraints (for example python=3.9) and can also reference a separate pip section for Python packages installable via PyPI. Example:

name: myenv

channels:

- conda-forge

dependencies:

- python=3.9

- numpy

- pandas

- pip

- pip:

- pytest

Creating an environment from the file is done with conda env create -f environment.yml. Activating the environment uses conda activate myenv. The file can be updated with conda env update -f environment.yml --prune to reflect changes. Exporting an environment’s current state back to a file is possible via conda env export > environment.yml, which helps with version control and collaboration.

Notes: environment.yml is a convenience for reproducibility in projects using Conda or Miniconda. While primarily associated with Conda, the approach—declaring dependencies in a structured YAML file—appears in other tools as well. Using pinned versions and clear channels improves determinism across systems.