pylinearfold

This project provides minimal Python bindings to both LinearFold and LinearPartition into one Python package, in ViennaRNA mode. The package can be installed from PyPI as wheels - not requiring any C++ compiler toolchain at the end user.

Installation

Install pylinearfold directly from PyPI:

python -m pip install pylinearfold

Supported Python versions: Python 3.10 and newer. Wheels are provided on PyPI for common platforms; if a wheel is not available for your platform you will need a C++ compiler toolchain to build from source.

🚀 Features

• ⚡ Linear-time RNA folding (fold)

• 🔬 Partition function & base-pair probabilities (partition)

• 🧬 MEA structure prediction (from LinearPartition)

• 🐍 Pure Python interface (thin bindings to the original C++ libraries)

• 💻 Works in Python scripts, notebooks, and pipelines

Quick Start

from pylinearfold import fold, partition
seq = "AUCGGUUCGCCGAU"

# Minimum free energy structure
result = fold(seq)

print(result["structure"])      # (((((....)))))
print(result["free_energy"])    # -4.2

# MEA structure, partition function energy and base pair probabilities
res = partition(seq)

print(res["structure"])       # (((((....)))))
print(res["free_energy"])     # -4.472184621676477
print(res["probabilities"])

API

Fold signature:

fold(
    seq: str,                   # RNA sequence
    beamsize: int = 100,        # beam size for beam search
    verbose: bool = False,      # verbose logging
    sharpturn: bool = False,    # enable sharp turn constraint
    zuker: bool = False,        # enable Zuker suboptimal structures
    delta: float = 5.0,         # delta parameter for Zuker exploration
    dangles: int = 2,           # dangles model (0, 1, or 2)
) -> dict

Returns a dict:

{
    "structure": str,       # dot-bracket string
    "free_energy": float,   # kcal/mol
}

Partition signature:

Python signature exposed by your bindings:

partition(
    seq: str,                   # RNA sequence
    beamsize: int = 100,        # beam size for beam search
    verbose: bool = False,      # verbose logging
    sharpturn: bool = False,    # enable sharp turn constraint
    cutoff: float = 1e-5,       # cutoff for base pair probabilities
    gamma: float = 1.0,         # gamma parameter for MEA structure
) -> dict

Returns a dict:

{
    "structure": str,               # MEA or partition-based structure (dot-bracket)
    "free_energy": float,           # partition function free energy
    "probabilities": np.ndarray,    # array of (i, j, prob)
}

Where probabilities is a NumPy structured array with dtype:

[('i', np.int32), ('j', np.int32), ('prob', np.float32 or np.float64)]

Each row represents a base pair (i, j) with pairing probability prob. The indexes i and j are 0-based (the first nucleotide has index 0).

Example (dtype and sample):

import numpy as np
probs = np.array([(0, 5, 0.8125), (1, 4, 0.1234)],
                 dtype=[('i', 'i4'), ('j', 'i4'), ('prob', 'f4')])
print(probs[0])         # (0, 5, 0.8125)

Quick use example (filtering high-probability pairs):

for i, j, p in probs:
    if p > 0.5:
        print(f"pair: {i}-{j}, prob={p:.2f}")

Note: the i and j coordinates are 0-based; add +1 if you prefer 1-based positions.

License

Please review the redistribution terms and warranty disclaimer in LICENSE.md. This project includes the original LinearFold/LinearPartition source and uses the same redistribution terms; see LICENSE.md for details.

Contributing

Issues and pull requests are welcome. If you plan to contribute, please open an issue first to discuss larger changes.

Citation

If you use pylinearfold in academic work, please cite the original LinearFold/LinearPartition papers:

• Liang Huang, He Zhang, Dezhong Deng, Kai Zhao, Kaibo Liu, David A Hendrix, David H Mathews, LinearFold: linear-time approximate RNA folding by 5'-to-3' dynamic programming and beam search, Bioinformatics, Volume 35, Issue 14, July 2019, Pages i295–i304, https://doi.org/10.1093/bioinformatics/btz375

• He Zhang, Liang Zhang, David H Mathews, Liang Huang, LinearPartition: linear-time approximation of RNA folding partition function and base-pairing probabilities, Bioinformatics, Volume 36, Issue Supplement_1, July 2020, Pages i258–i267, https://doi.org/10.1093/bioinformatics/btaa460