fitdecode

A FIT file parsing and decoding library written in Python (>= 3.6).

Usage Example

Read a FIT file, frame by frame:

import fitdecode

with fitdecode.FitReader('file.fit') as fit:
    for frame in fit:
        # The yielded frame object is of one of the following types:
        # * fitdecode.FitHeader (FIT_FRAME_HEADER)
        # * fitdecode.FitDefinitionMessage (FIT_FRAME_DEFINITION)
        # * fitdecode.FitDataMessage (FIT_FRAME_DATA)
        # * fitdecode.FitCRC (FIT_FRAME_CRC)

        if frame.frame_type == fitdecode.FIT_FRAME_DATA:
            # Here, frame is a FitDataMessage object.
            # A FitDataMessage object contains decoded values that
            # are directly usable in your script logic.
            print(frame.name)

Command line utilities

fitjson command converts a FIT file to JSON:

$ fitjson --pretty -o out_file.json in_file.fit

fittxt command converts a FIT file to human-readable text format convenient to ease FIT data inspection and debugging:

$ fittxt -o out_file.txt in_file.fit

Both commands accept a --filter option (or -f) which can be specified multiples times:

$ # include only RECORD messages:
$ fitjson -f=record -o out_file.json in_file.fit

$ # exclude FILE_ID and EVENT messages:
$ fitjson -f=-file_id -f=-event -o out_file.json in_file.fit

Installation

fitdecode is available on PyPI:

$ pip install fitdecode

Or, you can clone fitdecode's source code repository before installing it:

$ git clone [email protected]:polyvertex/fitdecode.git
$ cd fitdecode
$ pip install .

Note that for convenience, directory cmd located at the root of the project can safely be added to your PATH, such that fitdecode commands can be called without the package to be installed.

Overview

fitdecode is a non-offensive and incompatible rewrite of the fitparse library, with some improvements and additional features, thread-safety, and efforts to optimize both speed and memory usage.

Main differences between fitdecode and fitparse:

• fitdecode API is not compatible with fitparse
• fitdecode is faster
• fitdecode allows concurrent reading of multiple streams by being thread-safe, in the sense that fitdecode's objects keep their state stored locally
• fitdecode does not discard the FIT header and the CRC footer while reading a stream so that client code gets a complete 1:1 representation of the stream that is being read
• This also allows client code to easily deal with so-called chained FIT files, as per FIT SDK definition (i.e. concatenated FIT files)
• CRC computation and matching are both optional. CRC can be either matched, or only computed, or just ignored for faster reading.
• fitdecode offers optional access to records, headers and footers in their binary form, so to allow FIT file cutting, stitching and filtering at binary level

Why a new library?

A new library has been created instead of just offering to patch fitparse because many changes and adds in fitdecode break fitparse's backward compatibilty and because it allowed more freedom during the development of fitdecode.

Documentation

Documentation is available at https://fitdecode.readthedocs.io/

License

This project is distributed under the terms of the MIT license. See the LICENSE.txt file for details.

Credits

fitdecode is largely based on the generic approach adopted by fitparse to define FIT types and to decode raw values. That includes the module profile.py and all the classes it refers to, as well as the script generate_profile.py.