MacOS Python (version) chaos. shipped, MacPorts, official installer, anaconda

Soon after diving into python, I found out there were many versions of python co-existing in my MacOS, and I don't know how to manage them. It is a disaster for me.

After spending some time, here is what I found.

OS: macOS Catalina 10.15.3

• python installed by Apple:

      Don't change these files. Apple and other apps assumes their existences.

1. /usr/bin/python -> /System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
   may deprecate soon.
2. /usr/bin/python3
   it is a stub if it is a fresh install,  after full installation, it is v3.7.3.

• python installed by MacPorts:

1. /opt/local/bin/python   -> /opt/local/bin/python3.8
2. /opt/local/bin/python3 -> /opt/local/bin/python3.8 =>
       /opt/local/Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8
3. /opt/local/bin/python2 -> /opt/local/bin/python2.7 =>
       /opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
4. I upgraded 3.7 to 3.8, and set the path accordingly.
   sudo port install python38
   sudo port select --set python   python38
   sudo port select --set python3 python38
   export PATH=/opt/local/bin:/opt/local/sbin:/opt/local/libexec/gnubin:$PATH
   I found out that anaconda is easier to manage and use, or virtualenv if you prefer.

• python installed by python.org installer

1. /Library/Frameworks/Python.framework/Versions/3.8/bin/python3
   Uninstalled. https://docs.python.org/3/using/mac.html?highlight=uninstall
   I use Anaconda now.

• python installed by Anaconda  
  Anaconda is recommended for data science related development. Use virtualenv if you just need to manage python versions and library dependencies.

1. /Users/xxx/anaconda3/bin/python   (v3.7.x)
2. conda cheat sheet:
   activate default profile: conda activate
   activate a custom profile : conda activate XXX
   deactivate: conda deactivate
   create a custom profile: conda create -n XXX python
   create a custom profile with a specific python version: conda create -n XXX python=3.8.2
   install libs for a profile: conda activate XXX;  conda install pandas numpy jupyter
   search available pkgs/version: conda search python; conda search 'python>3.8'
   
   I treat every profile as a fresh installed python and use it both in VSCode and command line

Reference

1. https://apple.stackexchange.com/questions/376077/is-usr-bin-python3-provided-with-macos-catalina/376079#376079?s=ac24ad47437c4b85b0546bc3c4f00f23
2. https://gtbensmagazine.com/2019/05/07/the-right-and-wrong-way-to-set-python-3-as-default-on-macos/
3. https://www.anaconda.com/distribution/
4. https://github.com/conda/conda