Setting up programming environment is frustrating for newcomers. Although it is much easier than it was before, it’s still worth it to take note.

1. Apple developer tools

Not only the python development but all kinds of programming tasks on OSX require Apple developer tools. The instruction is easy; you download XCode from Mac AppStore, then you download Command Line Tools in the Downloads menu from the XCode Preference panel.

2. Homebrew

Next, install OSX most popular package manager homebrew. Just copy and paste this command in the terminal.

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ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"

If it shows an error about user permission, do the following

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cd /usr/local
sudo chown -R USER_NAME local

and setup environment variables in ~/.bash_profile (if the file does not exist, create one)

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export PATH="~/bin:/usr/local/share/python:/usr/local/bin:$PATH"

Now you can install the followings with homebrew.

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source ~/.bash_profile
brew install python --with-brewed-openssl
brew install gfortran
brew install freetype
brew install zmq

Years before Mountain Lion, I used to install fortran via High Performance Computing for Mac OSX, but it doesn’t work well with homebrew. Now it’s best to install everything with homebrew.

3. Python Virtualenv

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pip install virtualenv
mkdir ~/.virtualenvs ~/.pip
export VIRTUALENV_DISTRIBUTE=true
export PIP_VIRTUALENV_BASE=$HOME/.virtualenvs
export PIP_REQUIRE_VIRTUALENV=true
export PIP_DOWNLOAD_CACHE=$HOME/.pip/cache

cat <<END >> ~/.bash_profile
# virtualenv should use Distribute instead of legacy setuptools
export VIRTUALENV_DISTRIBUTE=true
# Centralized location for new virtual environments
export PIP_VIRTUALENV_BASE=$HOME/.virtualenvs
# pip should only run if there is a virtualenv currently activated
export PIP_REQUIRE_VIRTUALENV=true
# cache pip-installed packages to avoid re-downloading
export PIP_DOWNLOAD_CACHE=$HOME/.pip/cache
END

cd ~/.virtualenvs
virtualenv data-scientists
source data-scientists/bin/activate
echo "source $HOME/.virtualenvs/data-scientists/bin/activate" >> ~/.bash_profile

Now, if you type which pip it should print /Users/YOUR_HOME/.virtualenvs/data-scientists/bin/pip.

Install scipy, numpy, ipython, and matplot.

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pip install numpy
pip install scipy
pip install ipython
pip install matplotlib
pip install pandas
pip install tornado
pip install pyzmq
pip install ipython

Finally, install opencv

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brew tap homebrew/science
brew install opencv

If you want a additional nice GUI application for ipython, you can download it from IPython Notebook.

Trouble shooting

Sometimes homebrew has trouble with fetching the source code. If you found it is stuck on downloading the files, do the following

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brew install -v opencv

It will show the URL of the file it is going to download. Stop the command with ctrl-c, paste the URL to your browser and download it. After the download is complete, move the file to /Library/Cache/Homebrew.

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mv OpenCV-2.4.4a.tar.bz2 /Library/Caches/Homebrew/

Continue the installation by

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brew install opencv
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr . && make all install

Reference

1. Python and Virtualenv on Mac OSX Mountain Lion 10.8 - Hacker Codex
2. Virtualenv with numpy and scipy on Mac OSX - Calvin’s
3. Virtualenv 1.9.1 : Python Package Index