Skip to main content

A simple Nintendo BYML or BYAML v2/v3 parser and writer

Project description

Simple bymlv2 parser + writer + converters


  • Supports v2, v3 and v4 files. These versions are respectively used by The Legend of Zelda: Breath of the Wild and Super Mario Odyssey.
  • Supports 64-bit node types which are used in Super Mario Odyssey.
  • Supports both endianness. The little-endian format is used on the Switch.
  • Cross platform.
  • Easy to edit and readable output. No ugly XML. Unobtrusive type information.

Quick usage

Install Python 3.6+, then run pip install byml.

The C module for PyYAML is currently a hard dependency. If you are on Windows, you don't have to do anything special. If you are on Linux or on macOS, you will need to install libyaml.


byml_to_yml  PATH_TO_BYML    PATH_TO_YAML

If the byml is compressed, this tool will automatically decompress them.

To reuse the input file name and only change the extension, use !!.NEW_EXTENSION as the second argument.

Example: to convert to YAML in the same directory as the BYML, use byml_to_yml path_to_botw/Actor/ActorInfo.product.sbyml !!.yml


yml_to_byml  PATH_TO_YAML    PATH_TO_BYML

Add -b at the end if big endian should be used. For the Wii U version of Breath of the Wild, you must pass that flag.

To reuse the input file name and only change the extension, use !!.NEW_EXTENSION as the second argument.

If the target file extension starts with .s, the tool will automatically compress the BYML using yaz0.

Note about YAML integers/floats

  • !u before an integer indicates that the value is unsigned. In general, you should keep the signedness unchanged.

  • !l is for signed 64 bit values. (Not used in BotW.)

  • !ul is for unsigned 64 bit values. (Not used in BotW.)

  • !f64 is for binary64 floating point values. (Not used in BotW.)

Advanced usage

By default, if the destination argument is not specified, output will be sent to stdout, which is handy for looking at bymls without creating temporary files.

Library usage

import byml

parser = byml.Byml(raw_bytes)
document = parser.parse()

writer = byml.Writer(document, be=big_endian_mode, version=byml_version)


This software is licensed under the terms of the GNU General Public License, version 2 or later.

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distributions

No source distribution files available for this release.See tutorial on generating distribution archives.

Built Distribution

byml-2.4.4-py3-none-any.whl (16.4 kB view hashes)

Uploaded py3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page