FEniCS/dolfinx

Introduce enum `FileMode` for I/O file mode

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#4,366 opened on Aug 5, 2026

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good first issueio

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Description

Currently the file mode in which an output file is opened is specified by a string.

with XDMFFile(mesh.comm, filename, "w", encoding=encoding) as file:
        file.write_mesh(mesh)

This should be altered to be enum based and back end independent, ref. https://github.com/FEniCS/dolfinx/pull/4177#discussion_r3608425522.

Contributor guide

Research direction
Investigate all current uses of string based file modes in the I/O module, and design an enum based replacement that is backend independent, referencing the linked discussion for context.
Tech stack
python
Domain
api
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75