#!/usr/bin/env python
# coding: utf-8

# # Reading and writing Cosmology objects
# 
# In this notebook, we show a few usage examples for how to read and write `Cosmology` objects to disk.

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from pyccl import Cosmology


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cosmo = Cosmology(Omega_c=0.25, Omega_b=0.05, sigma8=0.8, h=0.7, n_s=0.96)
print(cosmo.__doc__)


# ## Serialization (writing parameters to disk)
# 
# Cosmology objects can be saved to a YAML format using the `write_yaml` method. This format is not currently very robust -- the exact order of the parameters must be maintained or the object cannot be read back in.

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cosmo.write_yaml('example_params.yaml')
get_ipython().system('cat example_params.yaml')


# ## Deserialization (reading parameters from disk)
# 
# The parameters can be read back in using the `read_yaml` *class method*. Note that this must be called on the `Cosmology` class itself, as shown below, and not an instance of the class.

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cosmo2 = Cosmology.read_yaml("example_params.yaml")


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print(cosmo2)


# This `Cosmology` object can then be used to obtain cosmological predictions. See the other examples in this directory, for example *Distance Calculations Example.ipynb* or the more comprehensive demo *SLAC Feb2018 Demo.ipynb*.

# # Using Python Pickle
# 
# `Cosmology` objects are also pickle-able, to make them easy to store on disk and to pass around in MPI environments.

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import pickle

with open('cosmo.pkl', 'wb') as fp:
    pickle.dump(cosmo2, fp)


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with open('cosmo.pkl', 'rb') as fp:
    cosmo3 = pickle.load(fp)

print(cosmo3)


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