I realized I had an outdated numpy version:
$ python
Python 2.7.10 (default, Oct 23 2015, 18:05:06)
[GCC 4.2.1 Compa         
        @Claudiu's solutions works pretty well, a little bit more cleaner would be:
python3 -m site --user-base
e.g. something like this in your .profile:
PATH="$(python3 -m site --user-base)/bin:${PATH}"
                                                                        As per the Python docs, this is installing using the "user scheme":
Files will be installed into subdirectories of site.USER_BASE (written as userbase hereafter).
You can see your USER_BASE value like this:
$ python -c "import site; print(site.USER_BASE)"
/Users/csaftoiu/Library/Python/2.7
I found that on my machine, this was on sys.path, but it came after the global install directories.
I solved it by adding this to my ~/.bash_profile:
# add user base to python path
export PYTHONPATH=$(python -c "import site, os; print(os.path.join(site.USER_BASE, 'lib', 'python', 'site-packages'))"):$PYTHONPATH
Now the latest version is indeed loaded:
$ python
Python 2.7.10 (default, Oct 23 2015, 18:05:06)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy
>>> numpy
<module 'numpy' from '/Users/csaftoiu/Library/Python/2.7/lib/python/site-packages/numpy/__init__.pyc'>
>>> numpy.version.full_version
'1.11.1'
>>>
                                                                        I installed packages with sudo pip install --user option and I had to do sudo python to get it working.
vishnu$ echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
With sudo:
vishnu$ sudo python
Python 2.7.10 (default, Jul 15 2017, 17:16:57) 
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.31)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import rasa_core
>>> 
Without sudo:
vishnu$ python
Python 2.7.10 (default, Jul 15 2017, 17:16:57) 
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.31)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import rasa_core
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named rasa_core
PS: I am running these on Mac OS High Sierra and my issue was with rasa_core and dependent packages.