[python] Does `anaconda` create a separate PYTHONPATH variable for each new environment?

I am starting to work with the Python Anaconda distribution from Continuum.io to do scipy work.
I have been able to get Anaconda up and running, but I cannot tell whether Anaconda creates a new PYTHONPATH environment variable for each new environment it creates, or whether it relies on the common system PYTHONPATH.

I could not find any information on this in the documentation.

Further, when I did a printenv, I did not see a PYTHONPATH variable in the newly created environment --though I did find a few new anaconda created environment variables.

The best I can find is that Anaconda added some Anaconda directories and the new environment directory to the head of PATH variable --but this does not necessarily isolate the new package from the system environment but it is close.

Does anyone know the answer to this question or found a way to deal with this concern?

This question is related to python scipy environment-variables anaconda

The answer is


Anaconda does not use the PYTHONPATH. One should however note that if the PYTHONPATH is set it could be used to load a library that is not in the anaconda environment. That is why before activating an environment it might be good to do a

unset PYTHONPATH

For instance this PYTHONPATH points to an incorrect pandas lib:

export PYTHONPATH=/home/john/share/usr/anaconda/lib/python
source activate anaconda-2.7
python
>>>> import pandas as pd
/home/john/share/usr/lib/python/pandas-0.12.0-py2.7-linux-x86_64.egg/pandas/hashtable.so: undefined symbol: PyUnicodeUCS2_DecodeUTF8
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/john/share/usr/lib/python/pandas-0.12.0-py2.7-linux-x86_64.egg/pandas/__init__.py", line 6, in <module>
    from . import hashtable, tslib, lib
ImportError: /home/john/share/usr/lib/python/pandas-0.12.0-py2.7-linux-x86_64.egg/pandas/hashtable.so: undefined symbol: PyUnicodeUCS2_DecodeUTF8

unsetting the PYTHONPATH prevents the wrong pandas lib from being loaded:

unset PYTHONPATH
source activate anaconda-2.7
python
>>>> import pandas as pd
>>>>

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