py2opsin
Simple Python interface to OPSIN: Open Parser for Systematic IUPAC nomenclature
Decision gist · record as of 2026-08-14
Yes. py2opsin is actively maintained, has no known vulnerabilities, low install friction, and a permissive MIT license. It solves a real problem (batch IUPAC-to-structure conversion) faster and more reliably than network-based alternatives. Install it if you work with chemical nomenclature and need local, offline name resolution; the only prerequisite is Java 8+.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Java 8 or later must be installed and available on the system PATH to execute OPSIN at runtime.
- Low friction: pure Python wheel with a single runtime dependency (typing_extensions).
- OPSIN v2.9.0 is bundled, so no external Java installation is needed at install time, though Java 8+ is required at runtime.
License · maintenance · safety
MIT (permissive) — MIT license permits unrestricted use, modification, and distribution in commercial and private projects, with only attribution and license notice required.
last release 2026-03-16 (151 days) · last repo commit 2026-03-16 · 81 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 221,234 downloads/mo, #9,283 on PyPI
Alternatives
Verify before relying
from py2opsin import py2opsin
smiles = py2opsin("ethane", output_format="SMILES")
# Returns: "CC"
# Batch processing (recommended for multiple names):
smiles_list = py2opsin(["pyridine", "aniline"], output_format="SMILES")- Whether the bundled OPSIN v2.9.0 is the latest available version and how frequently it is updated.
- Performance characteristics for very large batch operations (thousands+ of molecules).
- Behavior and error handling when Java is not available or OPSIN fails unexpectedly.
What it is and what it does
py2opsin is a lightweight Python wrapper around OPSIN, an open-source chemical nomenclature parser. It translates IUPAC chemical names into standardized molecular representations like SMILES, InChI, and CML. The package bundles OPSIN v2.9.0, so installation requires only Python and a runtime Java 8+ environment; it has minimal Python dependencies (only typing_extensions).
The primary use case is batch conversion of chemical names to structures, which is dramatically faster than making individual network requests to external services. The package accepts single names or lists of names and supports multiple output formats and parsing options (acid interpretation, radical handling, stereochemistry strictness). It is designed for cheminformatics workflows where you need to resolve chemical nomenclature locally without external API calls.
Use it for
- Convert a list of IUPAC names from a research paper into SMILES strings for molecular property analysis or machine learning.
- Batch-process chemical datasets where names are the primary identifier, converting them to canonical structures for downstream analysis.
- Resolve chemical nomenclature in automated workflows without relying on network calls or rate-limited external APIs.
- Explore chemical space by translating historical chemical names or nomenclature variants into modern structure formats.
- Support cheminformatics pipelines that require local, deterministic name-to-structure resolution with configurable parsing rules.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
py2opsin is actively maintained, has no known vulnerabilities, low install friction, and a permissive MIT license. It solves a real problem (batch IUPAC-to-structure conversion) faster and more reliably than network-based alternatives. Install it if you work with chemical nomenclature and need local, offline name resolution; the only prerequisite is Java 8+.
Install
py2opsin on PyPI
Before you install
Low friction: pure Python wheel with a single runtime dependency (typing_extensions). OPSIN v2.9.0 is bundled, so no external Java installation is needed at install time, though Java 8+ is required at runtime. Repository is active with recent commits.
Java 8 or later must be installed and available on the system PATH to execute OPSIN at runtime.
License in practice
MIT license permits unrestricted use, modification, and distribution in commercial and private projects, with only attribution and license notice required.
Quickstart
from py2opsin import py2opsin
smiles = py2opsin("ethane", output_format="SMILES")
# Returns: "CC"
# Batch processing (recommended for multiple names):
smiles_list = py2opsin(["pyridine", "aniline"], output_format="SMILES")Verify before relying
- Whether the bundled OPSIN v2.9.0 is the latest available version and how frequently it is updated.
- Performance characteristics for very large batch operations (thousands+ of molecules).
- Behavior and error handling when Java is not available or OPSIN fails unexpectedly.
Package facts
| License | MIT permissive |
| Python support | Supports the current Python release >=3.7 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 1 packagetyping_extensions |
| Maintenance | Actively maintained 151 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 221,234 / month, #9,283 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Programming Language :: Python :: 3 |
Evidence: py2opsin-1.2.0-py3-none-any.whl
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