===========
Quick Start
===========

Once installed, you can get a non-linear power spectrum prediction in just a few lines of Python.

The typical workflow involves:
1.  Creating a cosmology dictionary using the built-in helper function.
2.  Initializing the ``AletheiaEmu`` class.
3.  Calling the ``get_pnl()`` method with your wavenumbers, cosmology, and redshift.

.. note::
   The first time you run ``emu = AletheiaEmu()``, the package will automatically download the large model files (approx. 270-300 MB) to your computer's cache. This one-time download may take a few minutes. Subsequent runs will be fast.

.. code-block:: python

   import numpy as np
   from aletheiacosmo import AletheiaEmu

   # 1. Define cosmology using the built-in helper
   cosmo_params = AletheiaEmu.create_cosmo_dict(
       h=0.67,
       omega_b=0.0224,
       omega_c=0.120,
       n_s=0.96,
       A_s=2.1e-9,
       model='LCDM'
   )

   # 2. Initialize the emulator (this will be slow the first time)
   emu = AletheiaEmu()

   # 3. Get the non-linear P(k) at z=1.0
   k = np.logspace(-2, 0.3, 100)
   z = 1.0
   p_nonlinear = emu.get_pnl(k, cosmo_params, z)

   # The result is a NumPy array
   print(f"Calculated P(k) for {len(k)} k-points at z={z}.")