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NistChemPy 2.0.0 has changed the project’s data-distribution model.
Older PyPI releases of NistChemPy may contain bundled WebBook-derived index data, including nist_data.csv / nist_data.zip. Starting with NistChemPy 2.0.0, the package follows a software-only distribution model and no longer redistributes prebuilt NIST Chemistry WebBook / SRD 69 indexes, raw page caches, bulk extracted spectra, or other generated WebBook-derived data.
Instead, NistChemPy now provides local-index APIs and CLI tools that allow users to build or import local indexes from official WebBook pages. Generated indexes, caches, and downloaded records are user-local artifacts and are not part of the NistChemPy software distribution or software license.
Important
The main usability change is that broad local searches over all compounds with a given available property now require a local index. Users who previously relied on the bundled index should first build or import a local index and then use the same local-search workflows. Building a complete WebBook-scale index may take about 3.5-5+ days with a polite request delay, but this change keeps NistChemPy as a clean, redistributable software package rather than a redistribution channel for prebuilt WebBook-derived data.
Affected old PyPI release files are scheduled to be removed on June 1, 2026.
Users who need local WebBook indexes should use the documented local-index workflows in the current README and documentation.
Companion repository
The companion [NistChemData](https://github.com/muCommons/NistChemData) repository provides local reconstruction/download scripts built on top of NistChemPy. It should be treated as a workflow/script repository, not as a redistributed data archive.
Reason for the change
This change is intended to keep NistChemPy focused on redistributable software: parsers, APIs, CLI tools, tests, documentation, and small fixtures. WebBook-derived indexes and downloaded records should be generated locally by users from official WebBook pages, subject to applicable terms and policies.
NistChemPy 2.0.0 has changed the project’s data-distribution model.
Older PyPI releases of NistChemPy may contain bundled WebBook-derived index data, including
nist_data.csv/nist_data.zip. Starting with NistChemPy 2.0.0, the package follows a software-only distribution model and no longer redistributes prebuilt NIST Chemistry WebBook / SRD 69 indexes, raw page caches, bulk extracted spectra, or other generated WebBook-derived data.Instead, NistChemPy now provides local-index APIs and CLI tools that allow users to build or import local indexes from official WebBook pages. Generated indexes, caches, and downloaded records are user-local artifacts and are not part of the NistChemPy software distribution or software license.
Important
The main usability change is that broad local searches over all compounds with a given available property now require a local index. Users who previously relied on the bundled index should first build or import a local index and then use the same local-search workflows. Building a complete WebBook-scale index may take about 3.5-5+ days with a polite request delay, but this change keeps NistChemPy as a clean, redistributable software package rather than a redistribution channel for prebuilt WebBook-derived data.
Affected old PyPI release files are scheduled to be removed on June 1, 2026.
Recommended migration
Install or upgrade to the current release:
python -m pip install --upgrade "nistchempy>=2.0.0"Users who need local WebBook indexes should use the documented local-index workflows in the current README and documentation.
Companion repository
The companion
[NistChemData](https://github.com/muCommons/NistChemData)repository provides local reconstruction/download scripts built on top of NistChemPy. It should be treated as a workflow/script repository, not as a redistributed data archive.Reason for the change
This change is intended to keep NistChemPy focused on redistributable software: parsers, APIs, CLI tools, tests, documentation, and small fixtures. WebBook-derived indexes and downloaded records should be generated locally by users from official WebBook pages, subject to applicable terms and policies.
Thank you for your understanding.