python 2 instead of python 3 as the temporary default python

Question

on my computer     python -V  Python 3 2 1   but I get into problems when I run some python programs  my guess is  or at least I want to try this  that there is some backward compatibility issues  and I want to run those python scripts with    python2 2 7 2-2   which is also installed on my system but I do not know how to make it as the  temporary  default python  The python script starts with      usr bin env python   and I am using arch linux

User · Answer

As an alternative to virtualenv  you can use anaconda    On Linux  to create an environment with python 2 7   conda create -n python2p7 python 2 7 source activate python2p7   To deactivate it  you do   source deactivate   It is possible to install other package inside your environment

User · Answer

Use python command to launch scripts  not shell directly  E g     python2  usr bin command   AFAIK this is the recommended method to workaround scripts with bad env interpreter line

User · Answer

You could use alias python   usr bin python2 7    bash-3 2  alias bash-3 2  python Python 2 7 6  v2 7 6 3a1db0d2747e  Nov 10 2013  00 42 54    GCC 4 2 1  Apple Inc  build 5666   dot 3   on darwin Type  help    copyright    credits  or  license  for more information   gt  gt  gt   D bash-3 2  alias python   usr bin python3 3  bash-3 2  python Python 3 3 3  v3 3 3 c3896275c0f6  Nov 16 2013  23 39 35    GCC 4 2 1  Apple Inc  build 5666   dot 3   on darwin Type  help    copyright    credits  or  license  for more information   gt  gt  gt

User · Answer

mkdir   bin PATH   bin  PATH ln -s  usr bin python2   bin python   To stop using python2  exit or rm   bin python

User · Answer

If you have some problems with virtualenv   You can use it   sudo ln -sf python2  usr bin python   and  sudo ln -sf python3  usr bin python

User · Answer

You can use virtualenv    Use this to create your temporary python  install     Assuming that is the correct path to the python interpreter you want to use   virtualenv -p  usr bin python2 7 --distribute temp-python    Type this command when you want to use your temporary python    While you are using your temporary python you will also have access to a temporary pip    which will keep all packages installed with it separate from your main python install    A shorter version of this command would be    temp-python bin activate  source temp-python bin activate    When you no longer wish to use you temporary python type deactivate   Enjoy

User · Answer

You don t want a  temporary default Python   You want the 2 7 scripts to start with   usr bin env python2 7   And you want the 3 2 scripts to begin with    usr bin env python3 2   There s really no use for a  default  Python   And the idea of a  temporary default  is just a road to absolute confusion   Remember      Explicit is better than Implicit

User · Answer

Just call the script using something like python2 7 or python2 instead of just python   So   python2 myscript py   instead of   python myscript py   What you could alternatively do is to replace the symbolic link  python  in  usr bin which currently links to python3 with a link to the required python2 2 x executable  Then you could just call it as you would with python 3

[python] python 2 instead of python 3 as the (temporary) default python?

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