When I upgraded my Mac to OS X Mavericks, a lot of utilities (like Python, virtualenv, Xcode) broke, and it was pretty stressful trying to get it all set back up. Hopefully this guide can spare you some of that pain.Note: I'm by no means a Linux or Mac expert, so please fork and let me know if anything is redundant, incorrect, or missing!

python_mavericks_guide.sh

# A guide to prevent pain and suffering while upgrading to OS X Mavericks
# This will vary greatly depending on system set up, so read the instructions carefully

# Back up Virtulenvs
####################

# Very important! 
# For each virtualenv you have, run "pip freeze > requirements.txt" while in the activated virtualenv 
# in order to prevent loss of dependencies during the upgrade.

# Install Mavericks
###################

# Go to the App Store and install Mavericks
# Takes about 15 - 20 mins including set up

# Test Configuration
####################

# See if anything broke during the upgrade - I obviously had errors here.

$ cd project/using/virtualenv
$ workon <myproject>
$ python <myproject.py>

# If everything works, you're good! Otherwise, continue...

# Reinstall Virtualenv
######################

$ cd /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/setuptools/command
$ python easy_install.py virtualenv

# Reinstall Xcode Command Line Tools
##################################

# Yes, for some reason Mavericks uninstalls command line tools...
# Make sure you get the latest version (5.0.1)

$ xcode-select --install

# Repair Homebrew
#################

# If you don't already have Homebrew, I highly recommend that you install it now (http://brew.sh/)
# It will make fixing Python much easier if you need to relink it

$ brew update
$ brew upgrade
$ brew doctor

# Reinstall Python (if necessary)
#################################

# Try python from the command line. If it works, congratulations! 
# Depending on your system set up, you may need to reinstall using Homebrew.

$ brew install python # if you have an error, it's already installed and there's no issue
$ brew unlink python
$ brew link --overwrite python

# Then, if you want to include Python 3 as well (recommended):
$ brew install python3 # same deal here
$ brew unlink python3
$ brew link --overwrite python3

# Reinstall virtualenv{,wrapper}
################################

$ sudo pip install virtualenv
$ sudo pip install virtualenvwrapper

# Reinstall requirements
########################

# You might need to reinstall pip requirements (usually not, but if you have any issues, do this):

$ cd path/to/project
$ mkvirtualenv <project>
$ pip install -r requirements.txt # you backed them up didn't you?

# Finish
########

# I hope this guide was helpful! 
# Please fork if you have any suggestions, or shoot me an email at [email protected].

Thank you @goldsmith and @kneufeld. Fixed a number of issues for me.