Verdandi is a generic C++ library for data assimilation. Verdandi is currently developed at INRIA. It aims at providing methods and tools for data assimilation. It is designed to be relevant to a large class of problems involving high-dimensional numerical models. To guarantee the highest performance, the library is implemented in C++. In addition, Verdandi provides a Python interface generated by Swig. Models implemented in Fortran, C, C++, Python, ... can be plugged to Verdandi using either a C++ or Python interface.