pip-tools vs virtualenv

pip-tools is a free set of command-line tools for keeping pinned pip-based packages current and making builds more predictable. Its two core commands are pip-compile and pip-sync. pip-compile generates requirements.txt files from pyproject.toml, setup.cfg, setup.py, or requirements.in, and can handle project and optional dependencies in pyproject.toml. It can also generate hashes for pip hash-checking mode. pip-sync installs, upgrades, or removes packages to make a virtual environment match a compiled requirements.txt file. Defaults can be configured in .pip-tools.toml or pyproject.toml, and pip-compile can be used as a pre-commit hook. The tools support Linux, macOS, and Windows, and the package requires Python 3.9 or later. Compilation results may differ across operating systems, Python versions, and implementations, so the project advises compiling separately for each target environment. The default backtracking resolver is described as more robust but generally slower; the legacy resolver is deprecated. pip-tools is distributed under the BSD License.

virtualenv has no write-up on Specifiction yet; its figures are above.