[user@My-MacBook-Pro ~]$ cd ~/foo/bar
[user@My-MacBook-Pro bar]$ which python3
/usr/local/bin/python3
[user@My-MacBook-Pro bar]$ virtualenv -p /usr/local/bin/python3 demo
Running virtualenv with interpreter /usr/local/bin/python3
Using base prefix '/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5'
New python executable in /Users/user/foo/bar/demo/bin/python3.5
Also creating executable in /Users/user/foo/bar/demo/bin/python
Installing setuptools, pip, wheel...done.
[user@My-MacBook-Pro bar]$ cd ./demo/
[user@My-MacBook-Pro demo]$ ls
bin  include  lib  pip-selfcheck.json
[user@My-MacBook-Pro demo]$ . ./bin/
activate          activate.fish     easy_install      pip               pip3.5            python-config     python3.5
activate.csh      activate_this.py  easy_install-3.5  pip3              python            python3           wheel
[user@My-MacBook-Pro demo]$ . ./bin/activate
(demo) [user@My-MacBook-Pro demo]$ pip install flask
Collecting flask
  Downloading Flask-0.11.1-py2.py3-none-any.whl (80kB)
    100% |████████████████████████████████| 81kB 1.4MB/s
Collecting click>=2.0 (from flask)
  Downloading click-6.6.tar.gz (283kB)
    100% |████████████████████████████████| 286kB 2.1MB/s
Collecting itsdangerous>=0.21 (from flask)
  Downloading itsdangerous-0.24.tar.gz (46kB)
    100% |████████████████████████████████| 51kB 6.8MB/s
Collecting Jinja2>=2.4 (from flask)
  Downloading Jinja2-2.8-py2.py3-none-any.whl (263kB)
    100% |████████████████████████████████| 266kB 2.6MB/s
Collecting Werkzeug>=0.7 (from flask)
  Downloading Werkzeug-0.11.10-py2.py3-none-any.whl (306kB)
    100% |████████████████████████████████| 307kB 2.2MB/s
Collecting MarkupSafe (from Jinja2>=2.4->flask)
  Downloading MarkupSafe-0.23.tar.gz
Building wheels for collected packages: click, itsdangerous, MarkupSafe
  Running setup.py bdist_wheel for click ... done
  Stored in directory: /Users/user/Library/Caches/pip/wheels/b0/6d/8c/cf5ca1146e48bc7914748bfb1dbf3a40a440b8b4f4f0d952dd
  Running setup.py bdist_wheel for itsdangerous ... done
  Stored in directory: /Users/user/Library/Caches/pip/wheels/fc/a8/66/24d655233c757e178d45dea2de22a04c6d92766abfb741129a
  Running setup.py bdist_wheel for MarkupSafe ... done
  Stored in directory: /Users/user/Library/Caches/pip/wheels/a3/fa/dc/0198eed9ad95489b8a4f45d14dd5d2aee3f8984e46862c5748
Successfully built click itsdangerous MarkupSafe
Installing collected packages: click, itsdangerous, MarkupSafe, Jinja2, Werkzeug, flask
Successfully installed Jinja2-2.8 MarkupSafe-0.23 Werkzeug-0.11.10 click-6.6 flask-0.11.1 itsdangerous-0.24
(demo) [user@My-MacBook-Pro demo]$ python
Python 3.5.1 (default, Jan 22 2016, 08:54:32)
[GCC 4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from flask import Flask
>>>