How to default Python3.8 on my Mac using Homebrew? - python-3.x

Question

I have updated my python 3 to the latest version 3.8:
brew search python
==> Formulae
app-engine-python gst-python python ✔ python#3.8 ✔
boost-python ipython python-markdown wxpython
boost-python3 micropython python-yq
==> Casks
awips-python kk7ds-python-runtime mysql-connector-python
But when I check the python3 version on my mac it still shows 3.7:
python3 --version
Python 3.7.6
how can I default python3 to the latest 3.8 version using Homebrew ?
Edit:
When I tried to use brew switch, it tells me I only installed python 3.7.6, but with last brew upgrade I'm pretty sure that python3.8.1 is installed with Homebrew
brew switch python 3.8.1
python does not have a version "3.8.1" in the Cellar.
python's installed versions: 3.7.6_1

Answer 1

Here is the solution:
If existing symlinks belong to python 3.7 you should unlink them:
brew unlink python
Basically all you need to do:
brew link --force python#3.8
OR force the link and overwrite all conflicting files:
brew link --force --overwrite python#3.8
OR if needed list all files that would be deleted:
brew link --overwrite --dry-run python#3.8
Thus you can switch to any python version available in the Homebrew repo.
Also check out this answer for pyenv usage

Answer 2

Ok, thanks to #gromgit from Homebrew community discussion (https://discourse.brew.sh/t/how-to-default-python-3-8-on-my-mac-using-homebrew/7050)
Here is the solution:
$ brew info python#3.8
python#3.8: stable 3.8.1 (bottled) [keg-only]
...
==> Caveats
Python has been installed as
/usr/local/opt/python#3.8/bin/python3
...
python#3.8 is keg-only, which means it was not symlinked into /usr/local,
because this is an alternate version of another formula.
If you need to have python#3.8 first in your PATH run:
echo 'export PATH="/usr/local/opt/python#3.8/bin:$PATH"' >> ~/.bash_profile
For compilers to find python#3.8 you may need to set:
export LDFLAGS="-L/usr/local/opt/python#3.8/lib"
For pkg-config to find python#3.8 you may need to set:
export PKG_CONFIG_PATH="/usr/local/opt/python#3.8/lib/pkgconfig"
I will stick to python (v3.7.6) at this time and wait for seamless upgrade of v3.8.1 in the future releases.

Answer 3

You might have to add python 3.8.1 to your PATH in your ~/.bash_profile and put it first so that it overrides previous installations. First find out where python 3.8.1 was installed, then add it to your path like this:
export PATH="/PATH_TO_PYTHON/:${PATH}"

Answer 4

I have a company Mac with Python 2.7 preinstalled to run older software.
$ brew install pyenv (successful)
$ pyenv install 3.9.2 (successful)
$ python --version
Python 2.7
$ pyenv global 3.9.2
$ python --version
Python 2.7
It still says Python 2.7, so, I did the following commands
pyenv init
eval "$(pyenv init -)"
$ python --version
Python 3.9.2
More details:
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