How do I switch back to python2 after Anaconda set python3 as the default?

debugcn Published at Dev

Piyush Deshmukh

Recently, I installed Anaconda3-2.5.0-Linux-x86_64.sh on my 15.04 and ended up with this!

:~$ python --version
Python 3.5.1 :: Anaconda 2.5.0 (64-bit)

:~$ python2 --version
Python 2.7.9

:~$ python3 --version
Python 3.5.1 :: Anaconda 2.5.0 (64-bit)

During the last moments of installation, I did enter something as yes in hurry, and I suppose it had to do something with this. (Ok, my fault, I should have handled that carefully, but I need help now, not criticism).

Screenshot

AFAIK this is definitely going to break other programs. What do I do now?

What I think could work.

Can this be done using aliases?

alias python=python2

But I ain't sure.

Nephente

I went through the installation in a VM, and the following happend.

The installer asks for an install location. Default is /home/myuser/anaconda3.

At the end you'll be asked

Python 3.5.1 :: Continuum Analytics, Inc.
creating default environment...
installation finished.
Do you wish the installer to prepend the Anaconda3 install location
to PATH in your /home/myuser/.bashrc ? [yes|no]
[no] >>> yes

Prepending PATH=/home/myuser/anaconda3/bin to PATH in /home/myuser/.bashrc
A backup will be made to: /home/myuser/.bashrc-anaconda3.bak

To restore the old behavior, go to your home directory and do

mv .bashrc-anaconda3.bak .bashrc

then start a new shell.

As you suggest, you could alias python=python2, but I find that a bit weird. I would

Restore the original .bashrc
Create (if it does not exist) ~/bin
Link ln -s ~/anaconda3/bin/python3 ~/bin/python3
[Prepend $HOME/bin to $PATH](Should already be set by default by ~/.profile)
Relogin.

That way, calling python3 will start the one from Anaconda.

An important point is, that the original /usr/bin/python is still there, and still points to python2.7. The ramifications of having python->python3 in your path depend on how a specific script is called.

If the shebang #!/usr/bin/python is used, like it probably is in all executables that ship with Ubuntu, nothing will change. On the other hand, for better portability #!/usr/bin/env python is sometimes used, which will now cause python3.5 to be called.

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edited at2021-07-10

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