MolOP

MolOP is a Python library and command-line tool for computational chemistry files. It reads existing Gaussian, ORCA, xTB, and structure files, detects their formats, and maps them into a common batch -> file -> frame object model.

MolOP does not run quantum-chemistry calculations. It reads calculation results, supports batch filtering and summaries, converts structures, and provides an automation-friendly API.

Data-flow overview

flowchart TB
    subgraph inputs["Different sources and file formats"]
        direction TB
        qm["Quantum-chemistry outputs<br/>Gaussian / ORCA / xTB / ..."]
        qminput["Quantum-chemistry inputs<br/>GJF / ORCA input / ..."]
        structure["Structure files<br/>XYZ / SDF / SMILES / ..."]
        future["Future formats<br/>register another reader"]
    end

    parser["MolOP AutoParser<br/>select a reader from file content"]
    batch["FileBatchModelDisk<br/>batch -> file -> frame<br/>common scientific-result containers"]

    subgraph tasks["Common downstream processing"]
        direction TB
        results["Read energies, vibrations, orbitals, and more"]
        summary["Build complete tables and filter batches"]
        export["Convert and export structures or input files"]
        workflow["Build custom analysis and automation workflows"]
    end

    qm --> parser
    qminput --> parser
    structure --> parser
    future --> parser
    parser --> batch
    batch --> results
    batch --> summary
    batch --> export
    batch --> workflow

• Start here

  Install MolOP and run a working example.

  Install and verify

• Use Python

  Read results, build summaries, and export structures.

  5-minute start

• Use the CLI

  Chain parsing, filtering, and export from the shell.

  CLI first steps

• Look up details

  Find formats, fields, configuration, and API members.

  Reference

Smallest runnable workflow

Python

from molop import AutoParser

batch = AutoParser("water_mp2.out", n_jobs=1)
frame = batch[0][-1]

print(batch[0].detected_format_id)
print(frame.energies.total_energy.m_as("hartree"))

Output

Text Only

orcaout
-74.999374598107

Use the bundled ORCA water example. Results are exposed through common fields; missing values remain None instead of being synthesized from absent source data.

Choose by task

Goal	Recommended entry
Read one file or a batch	Parse files
Read energies, thermochemistry, vibrations, orbitals, or NMR	Read calculation results
Build CSV/JSON summary tables	Batch summaries
Select normal, optimized, or transition-state results	Filter and select
Export XYZ, SDF, Gaussian, or ORCA input	Convert and export
Recover a molecular graph from coordinates	Structure recovery
Diagnose paths, formats, or native-library issues	Troubleshooting
Tune logging, parallelism, or structure recovery	Configuration

Supported scope

MolOP provides readers or writers for Gaussian log/fchk/input, ORCA output/input, xTB output, XYZ, SDF/MOL, SMILES, and CML-related workflows. See the format overview for exact fields, targets, and information boundaries.

Core data model

Text Only

input path or glob -> AutoParser -> batch -> file -> frame
                                      |       |
                                batch operations  one structure and result snapshot

Read Core concepts for object levels, frame selection, and lazy structure recovery.

Next step

Start with Install and verify, or go directly to the 5-minute start when an input file is ready.