Priors

import bilby
import numpy as np
from astropy.cosmology import FlatLambdaCDM
cosmo = FlatLambdaCDM(70,0.3)

Priors = {}

#----------------------------------------
# Prior(DL): dVc/dz
#----------------------------------------
x = np.linspace(1.e-3,10,1000)
d = cosmo.luminosity_distance(x).value
H = cosmo.H(x).value
Rc = d/(1+x)
priorD = 4*np.pi*Rc**2/H
xx = d/1.e3
yy = priorD/sum(priorD)
#----------------------------#----------------------------#----------------------------
d1 = cosmo.luminosity_distance(0.001).value / 1.e3 # Gpc
d2 = cosmo.luminosity_distance(5.0).value / 1.e3   # Gpc
Priors['DL']    = bilby.core.prior.Interped(name='DL',xx=xx,yy=yy,minimum=d1, maximum=d2)
Priors['iota']  = bilby.core.prior.Sine(name='iota', minimum=0, maximum=np.pi)
Priors['psi']   = bilby.core.prior.Uniform(name='psi',minimum=0, maximum=np.pi)
#----------------------------#----------------------------#----------------------------
Priors['alpha'] = bilby.core.prior.Uniform(name='alpha',minimum=-np.pi, maximum=np.pi)
Priors['beta']  = bilby.core.prior.Sine(name='beta',minimum=0, maximum=np.pi)
#----------------------------#----------------------------#----------------------------
xx = np.linspace(-90,90,10000)
yy = np.cos(xx*np.pi/180)
yy/=sum(yy)
Priors['RA']    = bilby.core.prior.Uniform(name='RA',minimum=-180, maximum=180) # deg unit
Priors['Dec']   = bilby.core.prior.Interped(name='Dec',xx=xx,yy=yy,minimum=-90, maximum=90) # deg unit
#----------------------------#----------------------------#----------------------------
Priors['m1']    = bilby.core.prior.Uniform(name='m1',minimum=0.1, maximum=100)
Priors['m2']    = bilby.core.prior.Uniform(name='m2',minimum=0.1, maximum=100)
#----------------------------#----------------------------#----------------------------
Priors['Mc']    = bilby.core.prior.Uniform(name='Mc',minimum=0.1, maximum=100)
Priors['eta']   = bilby.core.prior.Uniform(name='eta',minimum=1.e-3, maximum=1./4)
Priors['q']     = bilby.core.prior.Uniform(name='q',minimum=1.e-3, maximum=1.0)
#----------------------------#----------------------------#----------------------------
Priors['sx1']    = bilby.core.prior.Uniform(name='sx1',minimum=0, maximum=1.0)
Priors['sy1']    = bilby.core.prior.Uniform(name='sy1',minimum=0, maximum=1.0)
Priors['sz1']    = bilby.core.prior.Uniform(name='sz1',minimum=0, maximum=1.0)
Priors['sx2']    = bilby.core.prior.Uniform(name='sx2',minimum=0, maximum=1.0)
Priors['sy2']    = bilby.core.prior.Uniform(name='sy2',minimum=0, maximum=1.0)
Priors['sz2']    = bilby.core.prior.Uniform(name='sz2',minimum=0, maximum=1.0)
#----------------------------#----------------------------#----------------------------
Priors['phi_coal']  = bilby.core.prior.Uniform(name='phi_coal',minimum=0, maximum=2*np.pi)
Priors['t_coal']    = bilby.core.prior.Uniform(name='t_coal',minimum=0, maximum=3600) # 1 hour
#----------------------------#----------------------------#----------------------------

Make your own prior

To redefine your priors define a dictionary as bellow:

# Defining a new prior only for the luminosity distance:

x = np.linspace(1,5,1000) # dL values
y = x**2 # prior as power-law

new_priors = {}
new_priors['DL'] = x, y

res = gw.GWDALI( Detection_Dict = params,
     FreeParams     = FreeParams,
     detectors      = [det0,det1,det2,det3], # Einstein Telescope + Cosmic Explorer
     approximant    = 'TaylorF2_py',
     dali_method    = 'Doublet',
     sampler_method = 'nestle', # Same as Bilby sampling method
     new_priors     = new_priors,
     save_fisher    = False,
     save_cov       = False,
     plot_corner    = False,
     save_samples   = False,
     hide_info      = True,
     index          = 1,
     rcond          = 1.e-4,
     npoints=300) # points for "nested sampling" or steps/walkers for "MCMC"