# Xarray Internals Xarray builds upon two of the foundational libraries of the scientific Python stack, NumPy and pandas. It is written in pure Python (no C or Cython extensions), which makes it easy to develop and extend. Instead, we push compiled code to [optional dependencies](../getting-started-guide/installing.html.md#installing). The pages in this section are intended for: - Contributors to xarray who wish to better understand some of the internals, - Developers from other fields who wish to extend xarray with domain-specific logic, perhaps to support a new scientific community of users, - Developers of other packages who wish to interface xarray with their existing tools, e.g. by creating a backend for reading a new file format, or wrapping a custom array type.