---
id: pycosat
version: "0.6.6"
license: MIT
license_treatment: permissive
maintenance: active
---

# pycosat — bindings to picosat (a SAT solver)

License: permissive · Maintenance: active · Downloads: 241.6K/mo

## What it is and what it does

pycosat wraps PicoSAT, a mature C-based SAT solver, into Python bindings that run at the C level. When you import pycosat, the solver becomes part of your Python process, avoiding subprocess overhead. The package includes the picosat source code (from picosat-965.tar.gz) so no external installation is needed, but compilation during install is required.

You represent constraint problems as clauses—lists of integers where the sign indicates negation and the absolute value identifies a variable. The main API consists of `solve()`, which returns a single satisfying assignment or "UNSAT"/"UNKNOWN", and `itersolve()`, which yields all solutions as an iterator. Both support propagation limits, variable counts, and verbosity control. This makes it suitable for problems like configuration validation, logic puzzles, and constraint-based reasoning where you need to find or enumerate satisfying assignments.

Use it for:

- Solve constraint satisfaction problems like Sudoku or logic puzzles by encoding them as CNF clauses and finding valid variable assignments.
- Enumerate all possible solutions to a satisfiability problem using itersolve() to explore solution spaces efficiently.
- Validate software configurations or dependency constraints by encoding them as logical clauses and checking satisfiability.
- Build automated reasoning or planning systems that need to find variable assignments satisfying a set of logical constraints.
- Prototype SAT-based algorithms without the overhead of calling an external solver process.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Provides efficient Python bindings to PicoSAT, a C-based Boolean satisfiability (SAT) solver, allowing you to solve constraint satisfaction problems by finding variable assignments that satisfy logical clauses.

Yes, if you need a lightweight SAT solver integrated directly into Python and are willing to compile a C extension. The package is mature, actively maintained, permissively licensed, and has no known vulnerabilities. High install friction due to compilation is the main trade-off; avoid it if you prefer pure-Python dependencies or already have a preferred SAT solver.

## Install

pip install pycosat
uv add pycosat
poetry add pycosat

## Installing pycosat

Before you install: High install friction: the package requires compilation from source (C extension). Maintenance is active with recent commits, but the latest release is over two years old, which may indicate a stable but not actively developed state.

License in practice: MIT license is permissive and places no significant restrictions on use, modification, or redistribution in commercial or private projects.

Quickstart:

import pycosat
cnf = [[1, -5, 4], [-1, 5, 3, 4], [-3, -4]]
solution = pycosat.solve(cnf)
print(solution)  # [1, -2, -3, -4, 5]

# Or iterate over all solutions
for sol in pycosat.itersolve(cnf):
    print(sol)

Requires a C compiler and build tools to compile the C extension during installation. The picosat source is bundled, but compilation is necessary.

Verify before relying:

- Whether the package is actively maintained or in maintenance-only mode given the two-year gap since the last release.
- Performance characteristics compared to other SAT solvers for large-scale problems.
- Whether propagation limits and verbosity options are sufficient for typical use cases.

## Package facts

- License: MIT (permissive)
- Python support: unspecified
- Install friction: high
- Maintenance: active
- Downloads: 241.6K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

SAT solver python, boolean satisfiability solver, constraint satisfaction python, picosat bindings, CNF formula solver, logic puzzle solver, sat-solver, constraint-satisfaction, c-extension

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