# Detailed installation guide for macOS¶

This is a step-by-step guide intended for those unfamiliar with Python or the command-line (a.k.a. the “shell”).

A shell can be opened by opening a new tab in the Terminal app (located in Utilities). Text that is formatted like code is meant to be copied and pasted into the terminal (hit the Enter key to run the command).

The fist step is to install the versions of Python that we need. The most convenient way of doing this is to use the OS X package manager Homebrew. Install Homebrew by running this command:

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"  Now you should have access to the brew command. First, we need to install Python 2 and 3. Using these so-called “brewed” Python versions, rather than the version of Python that comes with your computer, will protect your computer’s Python version from unwanted changes that could interfere with other applications. brew install python python3  Then we need to ensure that the terminal “knows about” the newly-installed Python versions: brew link --overwrite python brew link --overwrite python3  Now that we’re using our shiny new Python versions, it is highly recommended to set up a virtual environment in which to install PyPhi. Virtual environments allow different projects to isolate their dependencies from one another, so that they don’t interact in unexpected ways. Please see this guide for more information. To do this, you must install virtualenvwrapper, a tool for manipulating virtual environments. This tool is available on PyPI, the Python package index, and can be installed with pip, the command-line utility for installing and managing Python packages (pip was installed automatically with the brewed Python): pip install virtualenvwrapper  Now we need to edit your shell startup file. This is a file that runs automatically every time you open a new shell (a new window or tab in the Terminal app). This file should be in your home directory, though it will be invisible in the Finder because the filename is preceded by a period. On most Macs it is called .bash_profile. You can open this in a text editor by running this command: open -a TextEdit ~/.bash_profile  If you get an error that says the file doesn’t exist, then run touch ~/.bash_profile first to create it. Now, you’ll add three lines to the shell startup file. These lines will set the location where the virtual environments will live, the location of your development project directories, and the location of the script installed with this package, respectively. Note: The location of the script can be found by running which virtualenvwrapper.sh. The filepath after the equals sign on the second line will different for everyone, but here is an example: export WORKON_HOME=$HOME/.virtualenvs
export PROJECT_HOME=\$HOME/dev
source /usr/local/bin/virtualenvwrapper.sh


After editing the startup file and saving it, open a new terminal shell by opening a new tab or window (or just reload the startup file by running source ~/.bash_profile).

Now that virtualenvwrapper is fully installed, use it to create a Python 3 virtual environment, like so:

mkvirtualenv -p which python3 <name_of_your_project>


The option -p which python3 ensures that when the virtual environment is activated, the commands python and pip will refer to their Python 3 counterparts.

The virtual environment should have been activated automatically after creating it. Virtual environments can be manually activated with workon <name_of_your_project>, and deactivated with deactivate.

Important: Remember to activate the virtual environment with the workon command every time you begin working on your project. Also, note that the currently active virtual environment is not associated with any particular folder; it is associated with a terminal shell. In other words, each time you open a new Terminal tab or terminal window, you need to run workon <name_of_your_project (with some extra setup, this can be done automatically; see here). When a virtual environment is active, your command-line prompt will be prepended with the name of the virtual environment in parentheses.

Once you’ve checked that the new virtual environment is active, you’re finally ready to install PyPhi into it (note that this may take a few minutes):

pip install pyphi


Congratulations, you’ve just installed PyPhi!

To play around with the software, ensure that you’ve activated the virtual environment with workon <name_of_your_project>. Then run python to start a Python 3 interpreter. Then, in the interpreter’s command-line (which is preceded by the >>> prompt), run

import pyphi


Optionally, you can also install IPython with pip install ipython to get a more useful Python interpreter that offers things like tab-completion. Once you’ve installed it, you can start the IPython interpreter with the command ipython.

Next, please see the documentation for some examples of how to use PyPhi and information on how to configure it.