Virtualenv: workon command not found

Solving this problem took two steps:

Add this to your .bashrc / .bash_profile / .zshrc:

# load virtualenvwrapper for python (after custom PATHs)
venvwrap="virtualenvwrapper.sh"
/usr/bin/which -s $venvwrap
if [ $? -eq 0 ]; then
    venvwrap=`/usr/bin/which $venvwrap`
    source $venvwrap
fi

Then use:

source .bash_profile
# or .bashrc / .zshrc

to reflect the changes.

Additionally, if the terminal still sometimes cant find workon, use source .bash_profile to reset and find it again.