Yes, the above answers are correct and works fine on Unix based systems like Linux & MAC OS X.
I tried to create virtualenv for Python2 & Python3 with the following commands.
Here I have used venv2 & venv3 as their names for Python2 & Python3 respectively.
Python2 »
MacBook-Pro-2:~ admin$ virtualenv venv2 --python=`which python2` Running virtualenv with interpreter /usr/local/bin/python2 New python executable in /Users/admin/venv2/bin/python Installing setuptools, pip, wheel...done. MacBook-Pro-2:~ admin$ MacBook-Pro-2:~ admin$ ls venv2/bin/ activate easy_install pip2.7 python2.7 activate.csh easy_install-2.7 python wheel activate.fish pip python-config activate_this.py pip2 python2 MacBook-Pro-2:~ admin$ MacBook-Pro-2:~ admin$ Python3 »
MacBook-Pro-2:~ admin$ virtualenv venv3 --python=`which python3` Running virtualenv with interpreter /usr/local/bin/python3 Using base prefix '/Library/Frameworks/Python.framework/Versions/3.6' New python executable in /Users/admin/venv3/bin/python3 Also creating executable in /Users/admin/venv3/bin/python Installing setuptools, pip, wheel...done. MacBook-Pro-2:~ admin$ MacBook-Pro-2:~ admin$ ls venv3/bin/ activate easy_install pip3.6 python3.6 activate.csh easy_install-3.6 python wheel activate.fish pip python-config activate_this.py pip3 python3 MacBook-Pro-2:~ admin$ Checking Python installation locations
MacBook-Pro-2:~ admin$ which python2 /usr/local/bin/python2 MacBook-Pro-2:~ admin$ MacBook-Pro-2:~ admin$ which python3 /usr/local/bin/python3 MacBook-Pro-2:~ admin$