This library provides general binary file parsing by interpreting documentation of a file structure and data types. By default, it supports basic data types like big-endian and little-endian integers, floats and doubles, variable length (delimited) strings, maps and bit fields (flags) and it can iterate over sub structures. Other data types are easily added. The file structure and the types are stored in nested dictionaries. The structure is separated from the types, this way multiple file formats using the same types (within one project for example) can be easily supported without much duplication. The design of the library is such that all operations can be reversed. This means that fully functional binary editing is possible using this implementation; first use the reader to convert a binary file to a serialised dictionary representation, this representation is easily edited using a text editor, and then use the writer to convert back to binary. This idea is implemented in two languages; Python and JavaScript. All main development is done in Python. We chose YAML as our preferred serialised dictionary format, but other serialisation formats (JSON for example) can be used too. Please see ReadTheDocs for the latest documentation.