NISPO is an open-source, RDKit-based Python package for generating IUPAC names of molecules. Generated names are designed to pass an OPSIN round-trip test, in which OPSIN parses the name back to the same molecular structure. The entire NISPO codebase was generated by OpenAI Codex using GPT-5.5.
pip install nispoNISPO requires Python 3.10 or newer.
Use smiles_to_iupac to convert a single SMILES string, or
smiles_to_iupac_batch to convert multiple SMILES strings at once:
from nispo import smiles_to_iupac, smiles_to_iupac_batch
smiles_to_iupac("CCO")
# 'ethanol'
smiles_to_iupac_batch(["CCO", "not-a-smiles"])
# ['ethanol', '']Unsuccessful conversions return an empty string (""). Batch conversion
preserves the number and order of the inputs.
NISPO achieved 98.1% OPSIN round-trip accuracy on a held-out benchmark of 103 million PubChem compounds. It is optimized for OPSIN round-trip validity rather than preferred IUPAC nomenclature, so generated names may differ from names listed in databases.
If you use NISPO in your work, please cite:
@article{runcie2026nispo,
title = {{NISPO}: Open-source {IUPAC} name generation tool},
author = {Runcie, Nicholas T. and Imrie, Fergus and Deane, Charlotte M.},
journal = {arXiv preprint arXiv:2607.26113},
year = {2026},
doi = {10.48550/arXiv.2607.26113}
}OPSIN is described in Lowe, D. M.; Corbett, P. T.; Murray-Rust, P.; Glen, R. C. Chemical Name to Structure: OPSIN, an Open Source Solution. Journal of Chemical Information and Modeling 2011, 51 (3), 739–753. https://doi.org/10.1021/ci100384d.
NISPO is released under the BSD 3-Clause License. See LICENSE.
This repository was developed using OpenAI Codex. The codebase is AI-generated and was created through an autonomous self-iteration process: Codex repeatedly ran the benchmark, inspected failures, updated the implementation, and reran the benchmark until high OPSIN round-trip accuracy was achieved.