nab

nab resolves Python project dependencies and writes a PEP 751 lock or pinned requirements. It can download resolved artifacts, but it does not install them.

Keep dependency ranges in pyproject.toml, use nab to select compatible versions, then review the lock before handing it to an installer. The lock includes transitive dependencies and records its target environments. Installing from it reuses the recorded selection; running nab again makes a fresh one.

Start with the Python and platform running nab, declare a deployment target, or lock a matrix of environments. Remote sources are read without building them by default; build policy controls when a backend may run.

Start with a task

• Make your first lock, then install its dependencies.

• Use a lock with pip, hashed requirements, or an offline wheelhouse.

• Configure a resolve and inspect effective values.

• Use local projects, git sources, multiple indexes, or workspaces.

• Use a direct archive source with a required digest.

• Reason about PEP 508 markers as sets of environments.

• Diagnose a failed resolve from its error and Diagnostics: section.

• Check the CLI, output formats, or cache.

• Embed the generic resolver in another tool.

Status

nab is experimental. The table below states the current boundary; feature pages carry their own stability warnings.

Area	Current boundary
Runtime	CPython 3.10 and newer. Other interpreters are not tested.
Commands	nab lock resolves and writes a lock. nab download resolves again and fetches artifacts. Neither command installs packages.
Sources	Simple indexes, local checkouts, declared git sources, hash-pinned .tar.gz archives, and workspace members. Project-root name @ git+... requirements are not resolved yet.
Output	PEP 751 pylock.toml, requirements with recorded index hashes, and requirements without those hashes.
Experimental features	Universal locks, multiple indexes, and workspaces. Their feature pages state the current boundary.
Embedding	nab-resolver has a path-stable public API. nab-markersets documents its supported surface but remains experimental; the other component APIs are experimental.

Tutorial

• Getting started

How-to guides

• Install nab
• Use a lock
• Use a local checkout as a source
• Use a direct archive source
• Add a VCS dependency
• Lock with multiple indexes
• Lock a workspace
• Embed the resolver in your own tool
• Reason about markers

Reference

• CLI
• Selecting what to lock
• Output formats
• Resolution failures
• Configuration
• Lockfiles
• Build policy
• On-disk cache

Explanation

• Universal resolution
• Conflicting extras and groups
• The six distributions

Project

• Contributing