Hachoir is a library written in Python which allows to see and edit a binary file (or any binary stream) field per field. A field is the most basic information: a number, a string of characters, a flag (yes/no), etc. Only supported formats can be opened, it's not a magic tool. It can be used to extract some information (eg. metadata), edit some fields of a file without the original program, or convert a file from one format to another.