title: How to link home brew python version and set it as default
body: <p>I just switched from MacPorts to HomeBrew. After installing all the required XCode versions and other software I tried installing python using homebrew: I think it successfully installed, but when I do <code>which python</code> it still shows me 2.7.3 which I think is the version shipped with Mountain Lion. </p>
  
  <pre><code>which python
  /usr/local/bin/python
  
  python --version
  Python 2.7.3
  </code></pre>
  
  <p>so I tried to install again</p>
  
  <pre><code>brew install python --framework --universal
  Warning: python-2.7.5 already installed, it's just not linked
  </code></pre>
  
  <p>But it says python 2.7.5 already install and not linked, I tried to do <code>brew link python</code> </p>
  
  <p>That led me to following message so, I have no idea what I should be doing: </p>
  
  <p>Linking /usr/local/Cellar/python/2.7.5... Warning: Could not link python. Unlinking...</p>
  
  <pre><code>Error: Could not symlink file: /usr/local/Cellar/python/2.7.5/bin/smtpd2.py
  Target /usr/local/bin/smtpd2.py already exists. You may need to delete it.
  To force the link and overwrite all other conflicting files, do:
    brew link --overwrite formula_name
  
  To list all files that would be deleted:
    brew link --overwrite --dry-run formula_name
  </code></pre>