============
Installation
============

You can install the ``AletheiaCosmo`` package directly from the Python Package Index (PyPI) using ``pip``.

From PyPI
---------

We recommend installing the package inside a dedicated Python virtual environment.

.. code-block:: bash

   pip install AletheiaCosmo

This command will automatically handle the installation of the required dependencies, which include:

* ``numpy``
* ``scipy``
* ``camb``
* ``scikit-learn``
* ``appdirs``
* ``skops``

From Source
-----------

If you want to modify the code or contribute to development, you can install the package from a local copy of the repository.

.. code-block:: bash

   # Clone the repository
   git clone https://gitlab.mpcdf.mpg.de/arielsan/aletheia.git
   cd aletheia

   # Install in editable mode
   pip install -e .

.. note::
   **First-Time Use: Model Download**

   The ``AletheiaCosmo`` package is lightweight, but it requires a set of large model files (approx. 270-300 MB) to run.
   
   The first time you initialize the emulator (e.g., ``emu = AletheiaEmu()``), these model files will be automatically downloaded from the GitLab repository and stored in a local cache directory on your computer.
   
   This one-time download may take a few minutes depending on your internet connection. All subsequent uses of the emulator will load the models from this cache and will be fast.