How to (and should I) put a path to user-installed python ahead of system-installed python?

I have a separate installation of Python 3.*, but the first python path in my $PATH variable is the path to system-installed Python. Is this how it should be?

I have added the path to user-installed Python using https://www.architectryan.com/2012/10/02/add-to-the-path-on-mac-os-x-mountain-lion/#.Uydjga1dXDg, and it was popped at the end of $PATH.

Do I understand correctly that, in the current situation, when I run pip, brew etc. on python3 from bash, the changes will be applied to system-installed Python?

The fix I have got so far is to run export PATH=/usr/local/bin:/usr/local/sbin:$PATH every time I want to install or update python, but it is not ideal.

NB: I went with pyenv solution as suggested by @bermudalocket. This pyenv tutorial was very useful.

Solution 1:

You can accomplish this by adding

export PATH="/path/to/python:"$PATH

to your ~/.zshrc (or ~/.bash_profile if you're not on Catalina).

I'd like to propose an alternative and suggest pyenv, available via Homebrew. You can set a specific Python version to be "global" (i.e. default everywhere) and/or "local" (i.e. using that version in a specific directory only).

E.g.:

brew install pyenv
pyenv global 2.7.16
cd ~/myProjects/MyProject
pyenv local 3.7.6

If you were to use Python in ~/myProjects/MyProject it will default to 3.7.6, and anywhere else 2.7.16:

cd ~/some/other/directory
python --version
>> Python 2.7.16

cd ~/myProjects/MyProject
python --version
>> Python 3.7.6

https://github.com/pyenv/pyenv#homebrew-on-macos

Solution 2:

I installed Python 3.8 for macOS using the installer from python.org, not homebrew which is also installed on my Mac but rarely used. I think the first three lines below to my ~/.bash_profile was automatically added by the installer from python.org.

With those, any changes I make using pip3 seem to affect only the 3.8 whereas those made via pip seem to affect only the 2.7 (which I believe comes installed with macOS). Because I did not use homebrew in installing Python 3.8 (or 2.7), I assume it is not relevant for either version of Python in my case. Hope these help.

# Setting PATH for Python 3.8
PATH="/Library/Frameworks/Python.framework/Versions/3.8/bin:${PATH}"
export PATH

# Setting PATH for Python 2.7
# I believe the two lines below were already in the file before the above were added
PATH="/Library/Frameworks/Python.framework/Versions/2.7/bin:${PATH}"
export PATH