How to set Python’s default version to 3.x on OS X?

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How to set Python’s default version to 3.x on OS X?

I’m running Mountain Lion and the basic default Python version is 2.7. I downloaded Python 3.3 and want to set it as default.

Currently:

$ python
    version 2.7.5
$ python3.3
    version 3.3

How do I set it so that every time I run $ python it opens 3.3?

Asked By: Marcus

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Answer #1:

Changing the default python executable’s version system-wide could break some applications that depend on python2.

However, you can alias the commands in most shells, Since the default shells in macOS (bash in 10.14 and below; zsh in 10.15) share a similar syntax. You could put
alias python=’python3′
in your ~/.profile, and then source ~/.profile in your ~/.bash_profile and/or your~/.zsh_profile with a line like:

[ -e ~/.profile ] && . ~/.profile

This way, your alias will work across shells.

With this, python command now invokes python3. If you want to invoke the “original” python (that refers to python2) on occasion, you can use command python, which will leaving the alias untouched, and works in all shells.

If you launch interpreters more often (I do), you can always create more aliases to add as well, i.e.:

alias 2='python2'
alias 3='python3'

Tip: For scripts, instead of using a shebang like:

#!/usr/bin/env python

use:

#!/usr/bin/env python3

This way, the system will use python3 for running python executables.

Answered By: Santosh Kumar

Answer #2:

You can solve it by symbolic link.

unlink /usr/local/bin/python
ln -s /usr/local/bin/python3.3 /usr/local/bin/python
Answered By: Shin Kim

Answer #3:

Open ~/.bash_profile file.

vi ~/.bash_profile

Then put the alias as follows:

alias python='python3'

Now save the file and then run the ~/.bash_profile file.

source ~/.bash_profile

Congratulation !!! Now, you can use python3 by typing python.

python --version

Python 3.7.3

Answered By: Ananta Chandra Das

Answer #4:

Go to terminal type:

alias python=python3.x

This will setup default python as python3.x

Answered By: Aditya

Answer #5:

I’m a little late to the game on this one, but I thought I should post an updated answer since I just encountered this issue for myself. Please note that this will only apply to a Mac-based setup (I haven’t tried it with Windows or any flavor of Linux).

The simplest way to get this working is to install Python via Brew. If you don’t have brew installed, you will need to do that first. Once installed, do the following in at the terminal:

brew install python

This will install Python 3. After it’s installed, run this:

ls -l /usr/local/bin/python*

You will see all of the links created by brew to its Python install. It will look something like this:

lrwxr-xr-x  1 username  admin  36 Oct  1 13:35 /usr/local/bin/python3@ -> ../Cellar/python/3.7.4_1/bin/python3
lrwxr-xr-x  1 username  admin  43 Oct  1 13:35 /usr/local/bin/python3-config@ -> ../Cellar/python/3.7.4_1/bin/python3-config
lrwxr-xr-x  1 username  admin  38 Oct  1 13:35 /usr/local/bin/python3.7@ -> ../Cellar/python/3.7.4_1/bin/python3.7
lrwxr-xr-x  1 username  admin  45 Oct  1 13:35 /usr/local/bin/python3.7-config@ -> ../Cellar/python/3.7.4_1/bin/python3.7-config
lrwxr-xr-x  1 username  admin  39 Oct  1 13:35 /usr/local/bin/python3.7m@ -> ../Cellar/python/3.7.4_1/bin/python3.7m
lrwxr-xr-x  1 username  admin  46 Oct  1 13:35 /usr/local/bin/python3.7m-config@ -> ../Cellar/python/3.7.4_1/bin/python3.7m-config

The first row in this example shows the python3 symlink. To set it as the default python symlink run the following:

ln -s -f /usr/local/bin/python3 /usr/local/bin/python

Once set, you can do:

which python

and it should show:

/usr/local/bin/python

You will have to reload your current terminal shell for it to use the new symlink in that shell, however, all newly opened shell sessions will (should) automatically use it. To test this, open a new terminal shell and run the following:

python --version
Answered By: sknight

Answer #6:

The following worked for me

cd /usr/local/bin
mv python python.old
ln -s python3 python
Answered By: Mayank Jain

Answer #7:

This worked for me. I added alias and restarted my terminal:

alias python=/usr/local/bin/python3
Answered By: toadead

Answer #8:

Go to ‘Applications’, enter ‘Python’ folder, there should be a bash script called ‘Update Shell Profile.command’ or similar. Run that script and it should do it.

Update: It looks like you should not update it: how to change default python version?

Answered By: CT Zhu

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