EnsembleSampler error

• emcee version: 2.2.1
• platform: Windows 7
• installation method (pip/conda/source/other?):pip

I'm having this message:
Traceback (most recent call last):

File "", line 1, in
runfile('C:/Users/Adriana/Anaconda3/Lib/site-packages/radvel/borrar ya.py', wdir='C:/Users/Adriana/Anaconda3/Lib/site-packages/radvel')

File "C:\Users\Adriana\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 827, in runfile
execfile(filename, namespace)

File "C:\Users\Adriana\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 110, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)

File "C:/Users/Adriana/Anaconda3/Lib/site-packages/radvel/borrar ya.py", line 18, in
sampler = emcee.EnsembleSampler(nwalkers, ndim, lnprob, args=[ivar])

File "C:\Users\Adriana\Anaconda3\lib\site-packages\emcee\ensemble.py", line 91, in init
super(EnsembleSampler, self).init(dim, lnpostfn, args=args,

TypeError: super(type, obj): obj must be an instance or subtype of type

This happens when I run:

import numpy as np
import emcee

def lnprob(x, ivar):
return -0.5 * np.sum(ivar * x ** 2)

ndim, nwalkers = 10, 100
ivar = 1. / np.random.rand(ndim)
p0 = [np.random.rand(ndim) for i in range(nwalkers)]

sampler = emcee.EnsembleSampler(nwalkers, ndim, lnprob, args=[ivar])
sampler.run_mcmc(p0, 1000)

Start with the minimal reproduction in the issue and inspect emcee/ensemble.py around line 91, where EnsembleSampler initialization fails. Reproduce the TypeError using emcee 2.2.1 on the reported environment, then determine the smallest supported fix and verify that the sample sampler setup runs successfully.