fit2gpx-lightning 0.1.1

Fast FIT to GPX converter - replacement for fit2gpx

fit2gpx-lightning ⚡

Simple replacement for the fit2gpx Python library with 400x performance improvements thanks to Rust and parallel processing. I closely mirrored the original fit2gpx API for easy adoption (with a few adaptations and additions).

My motivation here was to both expose the wonderful Rust fit2gpx in python to make it more accessible for those of us who are more comfortable scripting in python. The orignal python fit2gpx library is quite slow for bulk conversions and also doesn't have a simple way to process Garmin bulk exports, only Strava. Here, we fix both those issues

[!INFO] AI Disclaimer: I did use Claude Code for significant portions of the coding and documentation, though I made quite a few manual changes to the final output. I would categorize this as "AI assisted coding" not "Vibecoded." Could I have done this all myself? Yes. Would it have taken too long for me to bother doing. Also yes.

Features

• Convert .fit files to GPX format, one at a time or entire folder
• Extract all activity tracks as GPX from Strava bulk export ZIPs
  • Supports .fit, .fit.gz, .gpx.gz, and .gpx files in source ZIP
  • Inject activity names and types from activities.csv
• Extract and convert FIT files to GPX from Garmin bulk export ZIPs
  • Matches FIT files to activity metadata from summarizedActivities.json

Limitations

• We don't support output to pandas Dataframes, which the original fit2gpx library does.

Installation

pip install fit2gpx-lightning

I have tried to include pre-built wheels for common platforms (Linux x86_64, Linux aarch64, macOS x86_64, macOS arm64, Windows x86_64). If you have trouble installing, please open an issue with your platform details and I will see if I can add support.

Quick Start

Simple Conversion

from fit2gpx_lightning import fit_to_gpx, fit_to_gpx_bulk

# Convert a single file
fit_to_gpx('activity.fit', 'activity.gpx')

# Convert an entire directory 
# (processes immediate children only)
stats = fit_to_gpx_bulk('./fit_files/', './gpx_files/')
print(f"✓ Converted {stats['converted']} out of {stats['total']} files")
print(f"✗ Failed: {stats['failed']}")

Strava Export Processing

The strava_fit_to_gpx function not only converts .fit files, but also unzips and converts .fit.gz files, extracts .gpx.gz files, and copies .gpx.

Complete example processing a Strava export:

from fit2gpx_lightning import StravaConverter

# Initialize converter with your Strava export ZIP
# Download from: https://www.strava.com/athlete/delete_your_account
converter = StravaConverter('strava_export.zip')

# Step 1: Convert FIT files to GPX
stats = converter.strava_fit_to_gpx('./gpx_output/')
print(f"✓ Converted: {stats['converted']}")
print(f"✗ Failed: {stats['failed']}")

# Step 2: Add metadata (activity names, types) from activities.csv. In place modification
converter.add_metadata_to_gpx('./gpx_output/')

Garmin Export Processing

Complete example processing a Garmin export:

from fit2gpx_lightning import GarminConverter

# Initialize converter with your Garmin export ZIP
# Download from: https://www.garmin.com/account/datamanagement/exportdata.html
converter = GarminConverter('garmin_export.zip')

# Step 1: Convert to GPX with automatic metadata matching
# Matches FIT files to activities by timestamp (±10 second tolerance)
stats = converter.garmin_fit_to_gpx('./gpx_output/')
print(f"✓ Converted: {stats['converted']}")
print(f"✓ Matched with metadata: {stats['matched']}")
print(f"⚠ Unmatched: {stats['unmatched']}")
print(f"✗ Failed: {stats['failed']}")

# Optional: Update metadata for already-converted files
converter.add_metadata_to_gpx('./gpx_output/')

API Reference

View full API reference at

Performance

Benchmark converting my Strava export of 1354 activities.

Library	Time	Throughput	Speedup
fit2gpx (Python)	9 m 25.9s	2.7 files/s	1x (baseline)
fit2gpx-lightning	1.39s	971.8 files/s	406.1x

Performance improvements from:

• ✨ Rust's zero-cost abstractions
• 🔒 Memory safety without garbage collection
• ⚡ Parallel processing with Rayon
• 🚀 Efficient binary handling

Development

Building from Source

# Install Rust (if not already installed)
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Clone repository
git clone https://github.com/yourusername/fit2gpx-lightning
cd fit2gpx-lightning/fit2gpx-lightning

# Install maturin (Python build tool for Rust extensions)
pip install maturin

# Build and install in development mode
maturin develop --release

# Run tests
cargo test --all-features

Running Tests

Integration tests won't pass unless you download your data and move some .fit files to the test_data/ folder. Strava export zip should be named strava.zip and Garmin export zip should be named garmin.zip.

# Rust unit and integration tests
cargo test

# With output
cargo test -- --nocapture

# Specific test
cargo test test_strava

# Python tests (after maturin develop)
python -m pytest tests/

Contributing

Contributions are welcome! Here's how to get started:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Make your changes
4. Run tests (cargo test)
5. Commit (git commit -m 'Add amazing feature')
6. Push (git push origin feature/amazing-feature)
7. Open a Pull Request

For feature suggestions or errors, open an issue.

Changelog

v0.1.0 (2025-12-24)

Initial Release

• Core FIT to GPX conversion functions
• Strava export support (.fit.gz, activities.csv)
• Garmin export support (nested ZIPs, summarizedActivities.json)
• Parallel processing for bulk operations
• Metadata injection from CSV and JSON
• Python bindings via PyO3
• CI/CD pipeline for multi-platform wheels
• Comprehensive documentation and examples
• Unit testing in rust and integration testing in Python using full exports downloaded in December 2025.

Support

• Documentation: This README + inline code documentation
• Issues: GitHub Issues