How to set Pythons default version to 3.x on OS X?

How to set Pythons default version to 3.x on OS X?

Changing the default python executables 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

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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.

You can solve it by symbolic link.

unlink /usr/local/bin/python
ln -s /usr/local/bin/python3.3 /usr/local/bin/python

How to set Pythons default version to 3.x on OS X?

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