Is there a way to downgrade Xcode from 5.1 to 5.0.2? I am now running version 5.1 and it's giving me all kinds of headaches when I use python.
There is no need to "downgrade". Just download Xcode 5.0.2 from the Apple developer download pages, and install it. Give it a name different from Xcode 5.1's name (e.g. call it "Xcode 5.0.2") and they can happily live side by side.
To switch between which one is used to look for command line tools such as clang, use the Command Line Tools popup menu in the Locations pref pane. Thus for example I use Xcode 5.1 to write iOS apps, but if I want to build a Ruby gem I switch to the Xcode 5.0.2 command-line tools (because of the problems with the new version of clang, which barfs on command-line arguments it doesn't like).