Astropy cosmology issue, the cosmology.H(z) function is unitless

Question

I'm trying to work with astropy.cosmology. As the documentation says, when I use the Hubble parameter method it should give me a value with units - astropy.cosmology documentation

But it gives me just a number as can be seen here -

ohm@ohm-ThinkCentre-M57:~/projects/mucalc$ python
Python 2.7.3 (default, Sep 26 2013, 20:08:41) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from astropy import cosmology
>>> cosmology.core.set_current(cosmology.Planck13)
>>> H0 = cosmology.H(10**6)
>>> print H0
647883886243.0
>>> H0.value
ERROR: AttributeError: 'numpy.float64' object has no attribute 'value' [unknown]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'numpy.float64' object has no attribute 'value'
>>> 

What could be the issue?

Answer 1

Support for quantities was added in Astropy 0.3 (see here), so what you are seeing is the expected behavior for Astropy 0.2.x. Here is the output with 0.3:

In [1]: from astropy import cosmology

In [2]: cosmology.core.set_current(cosmology.Planck13)

In [3]: H0 = cosmology.H(10**6)

In [4]: print H0
6.47883897961e+11 km / (Mpc s)

Note that you can also do:

In [8]: from astropy.cosmology import Planck13

In [9]: print Planck13.H(10**6)
6.47883897961e+11 km / (Mpc s)

which is more concise.