---
id: resfo
version: "5.0.1"
license: LGPL-3.0-or-later
license_treatment: copyleft
maintenance: active
---

# resfo — A (lazy) parser and writer for reservoir simulator fortran output format.

License: copyleft · Maintenance: active · Downloads: 128.7K/mo

## What it is and what it does

resfo is a parser for the binary and ASCII output formats used by reservoir simulators, particularly opm flow. It reads files with extensions like .UNRST, .EGRID, .INIT (binary) and .FUNRST, .FEGRID, .FINIT (ASCII), extracting them as a sequence of named arrays. The package does not interpret the semantic meaning of array names—it simply returns tuples of name and numpy array, leaving interpretation to the caller.

The package depends only on numpy and typing_extensions, making it lightweight to install. It is classified as Mature and supports Python 3.10 through 3.14. The repository is actively maintained with recent commits, and the package carries no known security vulnerabilities.

Use it for:

- Extract grid geometry and properties from opm flow simulation output for post-processing or visualization
- Read reservoir simulator results into numpy arrays for numerical analysis or machine learning workflows
- Parse historical or archived simulation output files in binary or ASCII format for data recovery
- Integrate simulator output into automated workflows that require programmatic access to simulation results

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

resfo parses binary and ASCII output files from reservoir simulators (such as opm flow), extracting named arrays as numpy arrays for programmatic access.

Yes. resfo is a specialized, actively maintained parser with low install friction and no security issues. If you work with reservoir simulator output files (especially from opm flow), it directly solves the problem of extracting binary/ASCII data into usable arrays. The LGPL-3.0-or-later license requires attention if you plan proprietary distribution, but poses no barrier to internal or open-source use.

## Install

pip install resfo
uv add resfo
poetry add resfo

## Installing resfo

Before you install: Low friction: pure Python wheel with only numpy and typing_extensions as runtime dependencies. Actively maintained with a recent release and ongoing repository activity.

License in practice: Licensed under LGPL-3.0-or-later (copyleft). Derivative works and modifications must be distributed under compatible terms; proprietary use requires careful licensing review.

Quickstart:

pip install resfo

import resfo

for kw, arr in resfo.read("my_grid.egrid"):
    print(kw, arr.shape)

Verify before relying:

- Whether the package handles all variants of reservoir simulator output formats beyond opm flow
- Performance characteristics when parsing large binary files
- Availability of lazy-loading features mentioned in the summary

## Package facts

- License: LGPL-3.0-or-later (copyleft)
- Python support: unspecified
- Install friction: low
- Maintenance: active
- Downloads: 128.7K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

reservoir simulator output parser, fortran binary file reader, opm flow output parser, unrst egrid init parser, numpy array extraction fortran, reservoir-simulation, geoscience, binary-format

[View on SkillFed](https://skillfed.io/packages/resfo) · [View on PyPI](https://pypi.org/project/resfo/)