How can I install a previous version of Python 3 in macOS using homebrew?

How can I install a previous version of Python 3 in macOS using brew?

With the command brew install python I got the latest version of Python 3 (currently v3.7.0), but I want the last version of Python 3.6 (currently 3.6.5).

I have read about another package pyenv that can assist in handle different python installation, but this solution is not suitable for me.

Short Answer

To make a clean install of Python 3.6.5 use:

    brew unlink python # If you have installed (with brew) another version of python
    brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/f2a764ef944b1080be64bd88dca9a1d80130c558/Formula/python.rb

To recover a previously installed Python version:

    brew switch python 3.x.x_x # Ex. 3.6.5_1

Use brew info python to see what you have previously installed

Long Answer

There are two formulas for installing Python with Homebrew: [email protected] and python.
The first is for Python 2 and the second for Python 3.

Note: You can find outdated answers on the web where it is mentioned python3 as the formula name for installing Python version 3. Now it's just python!

By default, with these formulas you can install the latest version of the corresponding major version of Python. So, you cannot directly install a minor version like 3.6.

Solution:

With brew, you can install a package using the address of the formula, for example in a git repository.

    brew install https://the/address/to/the/formula/FORMULA_NAME.rb

Or specifically for Python 3

    brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/COMMIT_IDENTIFIER/Formula/python.rb

The address you must specify is the address to the last commit of the formula (python.rb) for the desired version. You can find the commint identifier by looking at the history for homebrew-core/Formula/python.rb

https://github.com/Homebrew/homebrew-core/commits/master/Formula/python.rb

Python > 3.6.5

In the link above you will not find a formula for a version of Python above 3.6.5. After the maintainers of that (official) repository released Python 3.7, they only submit updates to the recipe of Python 3.7.

As explained above, with homebrew you have only Python 2 ([email protected]) and Python 3 (python), there is no explicit formula for Python 3.6.

Although those minor updates are mostly irrelevant in most cases and for most users, I will search if someone has done an explicit formula for 3.6.

From: stackoverflow.com/q/51125013