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.
I encountered this issue as well, so I thought I should post an updated answer. 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
You're all set now. But to make sure, do the following:
Run this command to reload your shell.
exec $SHELL -l
Once set, you can do:
which python
and it should show:
/usr/local/bin/python
You will have to reload your current terminal shell for it to use the new symlink in that shell, however, all newly opened shell sessions will (should) automatically use it. To test this, open a new terminal shell and run the following:
python --version
Go to 'Applications', enter 'Python' folder, there should be a bash script called 'Update Shell Profile.command' or similar. Run that script and it should do it.
Update: It looks like you should not update it: how to change default python version?
I believe most of people landed here are using ZSH thorugh iterm or whatever, and that brings you to this answer.
You have to add/modify your commands in ~/.zshrc instead.
Suggestions to alias python to python3 will cause problems with virtual environments that set the version of python (eg: pyenv). With pyenv, you can set the version globally like so:
pyenv global 3.8.2
and then in any specific project, you can create a .python-version file which has the python version inside of it:
pyenv local 2.7.1
This is the best way to manage multiple versions of python on a system in my opinion.
The RIGHT and WRONG way to set Python 3 as default on a Mac
In this article author discuss three ways of setting default python:
All these ways are working. You decide which is better.
I think when you install python it puts export path statements into your ~/.bash_profile file. So if you do not intend to use Python 2 anymore you can just remove that statement from there. Alias as stated above is also a great way to do it.
Here is how to remove the reference from ~/.bash_profile - vim ./.bash_profile - remove the reference (AKA something like: export PATH="/Users/bla/anaconda:$PATH") - save and exit - source ./.bash_profile to save the changes
Step-1: Upgrade python to latest version by: $ brew upgrade python
Step-2: Go to home: $ cd
Step-3: open .bash_profile
$ vi .bash_profile
PATH="/Library/Frameworks/Python.framework/Versions/3.8/bin:${PATH}" export PATH
Step-4: Save the file. And compile it by:
$ . .bash_profile
Step-5: Check the python version:
$ python -V
Step-6: Thats all.
I'm not sure if this is available on OS X, but on linux I would make use of the module command. See here.
Set up the modulefile correctly, then add something like this to your rc file (e.g. ~/.bashrc):
module load python3.3
This will make it so that your paths get switched around as required when you log in without impacting any system defaults.
If you use macports, you do not need to play with aliases or environment variables, just use the method macports already offers, explained by this Q&A:
How to: Macports select python
TL;DR:
sudo port select --set python python27
If you are using a virtualenvwrapper, you can just locate it using which virtualenvwrapper.sh, then open it using vim or any other editor then change the following
# Locate the global Python where virtualenvwrapper is installed.
if [ "${VIRTUALENVWRAPPER_PYTHON:-}" = "" ]
then
VIRTUALENVWRAPPER_PYTHON="$(command \which python)"
fi
Change the line VIRTUALENVWRAPPER_PYTHON="$(command \which python)" to VIRTUALENVWRAPPER_PYTHON="$(command \which python3)".
Well... It's kinda old. But still deserves a good answer.
And the good one is You Don't Wanna Touch The Default Python On Mac.
Install any Python version you need via Homebrew or whatever and use it in virtualenv. Virtualenv is often considered to be something crap-like, but it's still way, wayyyy better than changing python version system-wide (macOS is likely to protect itself from such actions) or user-wide, bash-wide... whatever. Just forget about the default Python. Using playgrounds like venv is what your OS will be most, very most grateful for.
The case is, for example, many modern Linux distributions get rid of Python2 installed out-of-the-box, leaving only Python3 in the system. But everytime you try to install something old with python2 as a dependency... hope you understand what I mean. A good developer doesn't care. Good developers create clean playgrounds with python version they desire.
This is the simplest way from my exp. (if you have brew installed on your mac).
Try this from your terminal:
brew install python3
and then run the below on your terminal :
ls -l /usr/local/bin/python*
Tip:
** (note down the python version 3.8 or 3.9 thats displayed on the terminal. This will be required in the next step). for e.g. in my case it was:
lrwxr-xr-x 1 user admin 24 May 7 14:33 /usr/local/bin/python -> /usr/local/bin/python3.9
Now run the below command on your terminal:
ln -s -f /usr/local/bin/python3.9 /usr/local/bin/python
(where 3.9 is the version displayed on your terminal with the previous command)
Its DONE !
To test your default version of python:
python --version
Happy Coding!
pyenv. - Shin Kim