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fimod

🐍🦀 fimod

🏗️ Mold your data, shape your CI, play with your pipelines 🪶 Python-powered molding without Python installed.

💡 DRY your pipelines · Slim your container images · Tame your configs

fimod (Flexible Input, Mold Output Data) embeds Pydantic Monty (a Rust implementation of Python) in a single binary (~2.3 MB, UPX-compressed). You write the transform logic; fimod handles parsing, format detection, and I/O.

# 🎯 One-liner
fimod s -i data.json -e '[u for u in data if u["active"]]'

# 📜 Reusable script
fimod s -i input.csv -m cleanup.py -o output.json

# 🔀 Format conversion
fimod s -i config.yaml -e 'data' -o config.toml

# 🔥 Fetch from URLs — no curl, no wget, no pipes!
fimod s -i https://api.github.com/repos/pytgaen/fimod -e 'data["name"]' --output-format txt

✨ Features

  • Python you already know

    No new DSL. Write for, if, comprehensions, string methods — it's just Python.

  • Single binary

    No runtime, no pip install, no dependencies. One ~2.3 MB binary (UPX-compressed) that works everywhere.

  • All the formats

    JSON · NDJSON · YAML · TOML · CSV · TXT · Lines — auto-detected from extension.

  • Batteries included

    re_* regex · dp_* dotpath · it_* iteration · hs_* hashing · msg_* logging · gk_* validation · env_subst — no imports needed.

  • 🚀 Awesome 🔥 Your input can be an HTTPS request!

    Awesome: -i https://... just works — fimod fetches (via reqwest with proxy and HTTPS support), parses, and transforms in one shot. Goodbye curl | jq!

🗺️ Guides

Start here if you're new to fimod.

  • Quick Start

    Install fimod and run your first transform in 2 minutes.

    Get started

  • Concepts

    The pipeline, Monty, molds, and the security model — how it all fits together.

    Understand fimod

  • Mold Scripting

    Write transforms with built-in regex, dotpath, iteration, and hash helpers.

    Write molds

  • CLI Reference

    All options and modes — slurp, check, no-input, in-place, args, debug, and more.

    Explore the CLI

📚 Reference

Lookup tables and complete specifications.

  • Formats

    JSON, NDJSON, YAML, TOML, CSV, TXT, Lines — behavior and options for each.

    Formats

  • Built-ins

    Complete signatures for re_*, dp_*, it_*, hs_*, msg_*, gk_*, env_subst, set_exit, set_input_format, set_output_format, set_output_file, args, headers.

    Built-ins

  • Mold Defaults

    # fimod: directives — embed format and option defaults directly in scripts.

    Mold Defaults

  • Exit Codes

    --check truthiness table and set_exit behavior explained.

    Exit Codes

🍳 Cookbook

Practical recipes — filtering, aggregation, regex, format conversion, validation, data generation, slurp, and more.

⚠️ Project Status

Early-stage software

fimod is young software, built with AI-assisted development ("vibe coding").

  • Monty is an early-stage Rust implementation of Python by Pydantic. Its API is unstable and may introduce breaking changes.
  • fimod depends directly on Monty and inherits that instability. Expect breaking changes as both projects mature.
  • Versioning follows Semantic Versioning — breaking changes bump the major version.
  • Built-in helpers (re_*, dp_*, it_*, hs_*, msg_*, gk_*, env_subst) are implemented in Rust to complement Monty's limited stdlib. In particular, regex functions use fancy-regex syntax (Rust/PCRE2 flavour), not Python's re module — see Built-ins → Regex.

Regex: Fimod built-ins vs Monty's re module

Fimod was originally built on Monty v0.0.6, which had no regex support. We introduced re_search, re_sub, re_findall, etc. as Fimod built-in functions to fill that gap — a good example of the challenges of moving fast alongside a young runtime.

Since Monty v0.0.8, import re works — Monty implements a subset of Python's re module. Both approaches now work side by side:

  • Fimod's re_* built-ins — direct access to fancy-regex, including advanced features like variable-length lookbehind/lookahead
  • import re — familiar Python API, but only partially implemented in Monty (also backed by fancy-regex under the hood)

The re_* built-ins are here to stay for the foreseeable future (at least until late 2027). As Monty's re module matures, we'll reconsider.

Since import re is already well-known to Python developers, the documentation focuses on the re_* built-ins which are specific to Fimod.