Make python3 as my default python on Mac

Before we make the changes, the default version of python in my system was python 2.7.17.

python --version

Python 2.7.17

To make python3 as default python by replacing python2 in Ubuntu.

1. Open Terminal
2. cd
3. nano ~/.bashrc
4. alias python=python3 (Add this line on top of .bashrc file)
5. Press ctr+o (To save the file)
6. Press Enter
7. Press ctr+x (To exit the file)
8. source ~/.bashrc OR . ~/.bashrc (To refresh the bashrc file)

python --version

Python 3.7.5

Changing the default python version system wide can break some applications that depend on python2. The alternative solution would be to create an alias.

If you are using zsh (the default on Mac OS) run the following from terminal:

echo 'alias python="python3"' >> ~/.zshrc

Probably the safest and easy way is to use brew and then just modify your PATH:

First update brew:

brew update

Next install python:

brew install python

That will install and symlink python3 to python, for more details do:

brew info python

Look for the Caveats:

==> Caveats
Python has been installed as
  /usr/local/bin/python3

Unversioned symlinks `python`, `python-config`, `pip` etc. pointing to
`python3`, `python3-config`, `pip3` etc., respectively, have been installed into
  /usr/local/opt/python/libexec/bin

Then add to your path /usr/local/opt/python/libexec/bin:

export PATH=/usr/local/opt/python/libexec/bin:$PATH

The order of the PATH is important, by putting first the /usr/local/opt/python/libexec/bin will help to give preference to the brew install (python3) than the one is in your system located in /usr/bin/python

According to this S.O. post, changing the default Python interpreter could possibly break some applications that depend on Python 2.

The post also refers to using aliasing as a solution, and this link might also be a good reference on how to do that.

Personally, I just type "Python3" before I run scripts or go into a shell environment instead of "python".