$ brew install python
$  which python
/usr/local/bin/python

# may need sudo below
$ pip install ydk ydk-models-ietf
$ python
Python 2.7.13 (default, Jul 18 2017, 09:17:00)
[GCC 4.2.1 Compatible Apple LLVM 8.1.0 (clang-802.0.42)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from ydk.models.ietf import ietf_interfaces as iif
Fatal Python error: PyThreadState_Get: no current thread
Abort trap: 6

$ git clone https://github.com/CiscoDevNet/ydk-py.git
$ cd ydk-py/core

# may need sudo for the below. Record files for later uninstall via "cat files.txt | xargs sudo rm -rf"
$ python setup.py install --record files.txt
$ cd ../ietf
$ python setup.py install --record files.txt

$ virtualenv venv
$ source venv/bin/activate
(venv) $ pip install ydk ydk-models-ietf
(venv) $ python
Python 2.7.13 (default, Jul 18 2017, 09:17:00)
[GCC 4.2.1 Compatible Apple LLVM 8.1.0 (clang-802.0.42)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from ydk.models.ietf import ietf_interfaces as iif
>>>