Basis
=====

Overview
--------
:class:`libintx.Basis` is a list-like container of (Gaussian, Atom) pairs.
It exposes convenience methods for AO indexing, normalization and provides
properties such as ``nao``, ``ncart`` and ``nspher``.

Constructor
-----------

.. code-block:: python

   Basis(shells=[])   # shells: list[libintx.data.Gaussian], atoms: list[list/array]

Properties & Methods
--------------------
* ``nao`` - total number of AOs in the basis.
* ``ncart`` - total number of Cartesian functions.
* ``nspher`` - total number of spherical functions.
* ``aos_by_shell()`` - return list of (start, end) AO index ranges for each shell.
* ``normalize(racah=True)`` - normalize shells (Racah normalization to match PySCF by default).

Examples
--------
.. code-block:: python

   from libintx.tools import pyscf_to_libintx_basis
   basis = pyscf_to_libintx_basis(mol).normalize()