Does anaconda create a separate PYTHONPATH variable for each new environment

Question

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

User · Accepted Answer

No  the only thing that needs to be modified for an Anaconda environment is the PATH  so that it gets the right Python from the environment bin  directory  or Scripts  on Windows    The way Anaconda environments work is that they hard link everything that is installed into the environment  For all intents and purposes  this means that each environment is a completely separate installation of Python and all the packages  By using hard links  this is done efficiently  Thus  there s no need to mess with PYTHONPATH because the Python binary in the environment already searches the site-packages in the environment  and the lib of the environment  and so on

User · Answer

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  gt  gt  gt  gt  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   lt stdin gt    line 1  in  lt module gt    File   home john share usr lib python pandas-0 12 0-py2 7-linux-x86 64 egg pandas   init   py   line 6  in  lt module gt      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  gt  gt  gt  gt  import pandas as pd  gt  gt  gt  gt

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

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