excel-slim

Excel file optimization with a Rust core and a Python-first API. The default path is lossless and deterministic, with optional lossy media optimization when explicitly enabled.

Highlights

• Python API: excel_slim.optimize() and excel_slim.analyze()
• CLI mirrors Python options (no subprocess in Python)
• Lossless by default, lossy media is opt-in
• Deterministic output (stable ordering, timestamps)
• Handles .xlsx and .xlsm (VBA pass-through)

Install

Python (published on PyPI)

pip install excel-slim

Python (from source)

python -m pip install maturin
maturin develop

CLI (from source)

cargo build -p excel-slim-cli --release
./target/release/excel-slim --help

Quick start

Python

import excel_slim

report = excel_slim.optimize(
    "input.xlsx",
    output="output.xlsx",
    profile="safe",
    xml=True,
    zip=True,
    vba="auto",
    media="off",
)

info = excel_slim.analyze("input.xlsm")

CLI

excel-slim input.xlsx --report
excel-slim input.xlsm --xml --zip --vba=auto --media=lossless --report=json

Python API

analyze

info = excel_slim.analyze("input.xlsx")

Returns a dict with:

• format: xlsx|xlsm|xls|csv|unknown
• size_bytes
• has_vba, has_media
• xml_stats: worksheets, shared strings size, styles size
• recommendations, risks

optimize

report = excel_slim.optimize(
    "input.xlsx",
    output="output.xlsx",
    profile="safe",        # safe | balanced | aggressive
    xml=True,               # XML optimizations
    zip=True,               # ZIP repack
    vba="auto",            # auto | off | on
    media="off",           # off | lossless | lossy
    report=True,
    report_format="dict",  # dict | json_string
)

optimize() returns an OptimizationReport with per-module savings and metadata.

Convenience API

from excel_slim import WorkbookOptimizer

opt = WorkbookOptimizer("input.xlsx")
opt.profile("safe").xml(True).zip(True).media("lossless")
report = opt.optimize("output.xlsx")

Profiles

• safe: fast, lossless only. Skips heavy XML passes.
• balanced: enables style pruning for additional savings.
• aggressive: enables XML minify and best compression (slowest).

Determinism

• Stable ZIP ordering
• Fixed timestamps
• Consistent compression settings by profile

Safety

• Never executes macros or formulas
• VBA streams are preserved as-is
• Zip entry validation prevents path traversal

Development

Requirements

• Rust 1.70+
• Python 3.8+
• maturin (python -m pip install maturin)

Build + test

cargo test
python -m pytest

Publish (PyPI)

This uses maturin to build and publish wheels.

maturin build --release
maturin publish --release

Set your token in the environment before publishing:

export MATURIN_PYPI_TOKEN="pypi-..."

Roadmap

See the engineering plan in the project brief for shared strings, styles pruning, VBA compression, media optimization, and XLS support phases.