How can I troubleshoot Python "Could not find platform independent libraries <prefix>"

If you made a virtual env, then deleted that python installation, you'll get the same error. Just rm -r your venv folder, then recreate it with a valid python location and do pip install -r requirements.txt and you'll be all set (assuming you got your requirements.txt right).

Try export PYTHONHOME=/usr/local. Python should be installed in /usr/local on OS X.

This answer has received a little more attention than I anticipated, I'll add a little bit more context.

Normally, Python looks for its libraries in the paths prefix/lib and exec_prefix/lib, where prefix and exec_prefix are configuration options. If the PYTHONHOME environment variable is set, then the value of prefix and exec_prefix are inherited from it. If the PYTHONHOME environment variable is not set, then prefix and exec_prefix default to /usr/local (and I believe there are other ways to set prefix/exec_prefix as well, but I'm not totally familiar with them).

Normally, when you receive the error message Could not find platform independent libraries <prefix>, the string <prefix> would be replaced with the actual value of prefix. However, if prefix has an empty value, then you get the rather cryptic messages posted in the question. One way to get an empty prefix would be to set PYTHONHOME to an empty string. More info about PYTHONHOME, prefix, and exec_prefix is available in the official docs.

change PYTHONHOME to the parent folder of the bin file of python, like /usr，which is the parent folder of /usr/bin.