The "verbose" Python
“Suddenly” (as is traditional to commence these sort of stories), I started having problems with some of the Python installations on my local machine. As is the way of things, I had three distinct sources of Python:
- The native / builtin Python that came with my Mac
- The Python that was installed by brew to support other brew applications
- The Pythons installed by anaconda
The symptoms were that some of these (notably anaconda) would complain about how they didn’t recognise PYTHONPATH or that they were seeing a package tree of a different version type (2.X) to their own version (3.x):
% python2.7 Python 2.7.6 (default, Sep 9 2014, 15:04:36) [GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> ^D % ~/anaconda/bin/python Error in sitecustomize; set PYTHONVERBOSE for traceback: KeyError: 'PYTHONPATH' Python 3.4.3 |Anaconda 2.1.0 (x86_64)| (default, Mar 6 2015, 12:07:41) [GCC 4.2.1 (Apple Inc. build 5577)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>>
Similar symptoms would occur if you called various python-related utilities: pip, condo, etc.:
% conda list Error in sitecustomize; set PYTHONVERBOSE for traceback: KeyError: 'PYTHONPATH'
Setting the verbose flag on Python invocation showed that, indeed, the error was originating from within a Python 2.7 library that was being seen by a 3.x version Python:
... # code object from /usr/local/lib/python2.7/site-packages/sitecustomize.py # created '/usr/local/lib/python2.7/site-packages/__pycache__/sitecustomize.cpython-34.pyc' # wrote '/usr/local/lib/python2.7/site-packages/__pycache__/sitecustomize.cpython-34.pyc'
- PYTHONPATH was being set in my .bash_profile so I deleted it. Nope.
- Maybe the compiled sitecustomize.py files had been corrupted? Delete them. Nope.
- Uninstall the brew python? Nope.
- Some of the error messages suggested unsetting PYTHONPATH. Nope.
Eventually this thread https://github.com/conda/conda/issues/448 gave me the clue. So I added this to my .bash_profile:
And then everything was fine.