Switch between python 2 7 and python 3 5 on Mac OS X

Question

I generally use Python 2 7 but recently installed Python 3 5 using Miniconda on Mac OS X  Different libraries have been installed for these two versions of python  Now  the entering either of the keywords  python  or  python3  in terminal invokes python 3 5  and  python2  returns  -bash  python2  command not found   How can I now invoke them specifically using aliases  python2  and  python3  respectively   I am currently using OS X El Capitan

User · Answer

I already had python3 installed via miniconda3  and needed to install python2 alongside in that case brew install python won t install python2  so you would need brew install python 2    Now alias python2 refers to python2 x from  usr bin python  and alias python3 refers to python3 x from  Users ishandutta2007 miniconda3 bin python  and alias python refers to python3 by default   Now to use python as alias for python2  I added the following to  bashrc file   alias python   usr bin python     To go back to python3 as default just remove this line when required

User · Answer

How to set the python version back to 2 7 if you have installed Anaconda3  Python 3 6  on MacOS High Sierra 10 13 5  Edit the  bash profile file in your home directory   vi  HOME  bash profile  hash out the line   export PATH   Users YOURUSERNAME anaconda3 bin  PATH   Close the shell open again you should see 2 7 when you run python   Then if you want 3 6 you can simply uncomment your anaconda3 line in your bash profile   Trying to unlink python will end in tears in Mac OSX   You will something like this  unlink   usr bin python  Operation not permitted  Hope that helps someone out

User · Answer

If you want to use Apple   s system install of Python 2 7  be aware that it doesn   t quite follow the naming standards laid out in PEP 394   In particular  it includes the optional symlinks with suffix 2 7 that you   re told not to rely on  and does not include the recommended symlinks with suffix 2 that you   re told you should rely on     If you want to fix this  while sticking with Apple   s Python  you can create your own symlinks     cd  lt somewhere writable and in your PATH gt    ln -s  usr bin python python2   Or aliases in your bash config   alias python2 python2 7   And you can do likewise for Apple   s 2to3  easy install  etc  if you need them   You shouldn   t try to put these symlinks into  usr bin  and definitely don   t try to rename what   s already there  or to change the distutils setup to something more PEP-compliant  Those files are all part of the OS  and can be used by other parts of the OS  and your changes can be overwritten on even a minor update from 10 13 5 to 10 13 6 or something  so leave them alone and work around them as described above     Alternatively  you could    Just use python2 7 instead of python2 on the command line and in your shbangs and so on   Use virtual environments or conda environments  The global python  python3  python2  etc  don   t matter when you   re always using the activated environment   s local python  Stop using Apple   s 2 7 and instead install a whole other 2 7 alongside it  as most of the other answers suggest   I don   t know why so many of them are also suggesting that you install a second 3 6  That   s just going to add even more confusion  for no benefit

User · Answer

OSX s Python binary  version 2  is located at  usr bin python  if you use which python it will tell you where the python command is being resolved to  Typically  what happens is third parties redefine things in  usr local bin  which takes precedence  by default over  usr bin   To fix  you can either run  usr bin python directly to use 2 x or find the errant redefinition  probably in  usr local bin or somewhere else in your PATH

User · Answer

I just follow up the answer from  John Wilkey   My alias python used to represent python2 7  located in  usr bin   However the default python path is now preceded by  usr local bin for python3  hence when typing python  I didn t get either the python version   I tried make a link in  usr local bin for python2   ln -s  usr bin python  usr local bin   It works when calling python for python2

User · Answer

Similar to John Wilkey s answer I would run python2 by finding which python  something like using  usr bin python and then creating an alias in  bash profile   alias python2   usr bin python   I can now run python3 by calling python and python2 by calling python2

User · Answer

IMHO  the best way to use two different Python versions on macOS is via homebrew  After installing homebrew on macOS  run the commands below on your terminal   brew install python 2 brew install python   Now you can run Python 2 7 by invoking python2 or Python 3 by invoking python3  In addition to this  you can use virtualenv or pyenv to manage different versions of python environments   I have never personally used miniconda but from the documentation  it looks like it is similar to using pip and virtualenv in combination

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