Mac OS X latest Yosemite comes with Python version 2.7, but not with pip (package manager). If you have Command Line Tools installed, the installation of pip is very simple.

Installation

# install command line tools (if not installed)
$ xcode-select --install

# install pip via easy_install
$ sudo easy_install pip

# show current pip version (optional)
$ pip --version

Upgrade

# show current pip version (optional)
$ pip --version

# upgrade pip
$ sudo pip install --upgrade pip

In case you need to install and manage different versions of Python, I can recommend to read this article.