After updating to MacOS Catalina, install Xcode Command Line Tools and change from Python 2.7 series to 3.7 series (bash)

• MacOS Catalina
• Python 2.7.17
• bash

After upgrading from MacOS Mojave to Catalina, numpy can no longer be imported. While improving this situation, at the same time, the Python 2 series was upgraded to 3.7.7 at this opportunity, although support will end in January 2020. I will describe how to do it as a memorandum in this article.

Error message indicating that numpy cannot be imported

$ python abc.py
Traceback (most recent call last):
  File "abc.py", line 3, in <module>
    import numpy as np
ModuleNotFoundError: No module named 'numpy'

Error trying to install Python

So I tried to install Python 3.7.7, but I got an error.

$ pyenv install 3.7.7
(Omitted)
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

I found a similar case study on different versions of the OS in another Qiita article. Corrective action for "xcrun: error: invalid active developer path (/ Library / Developer / CommandLineTools) ..." after updating macOS

Install Xcode Command Line Tools

I installed it because I need Xcode Command Line Tools. In my environment, I was able to proceed in the following way.

$ softwareupdate --list
Software Update Tool

Finding available software
Software Update found the following new or updated software:
* Label: Command Line Tools for Xcode-12.1
	Title: Command Line Tools for Xcode, Version: 12.1, Size: 431272K, Recommended: YES, 

$ softwareupdate --install -a
Software Update Tool

Finding available software

Downloading Command Line Tools for Xcode
Downloaded Command Line Tools for Xcode
Installing Command Line Tools for Xcode
Done with Command Line Tools for Xcode
Done.

Check the version of pyenv and the contents of .bash_profile

At this time, the version of pyenv is as follows.

$ pyenv --version
pyenv 1.2.17

The .bash_profile contained the following description:

(Omitted)
PYENV_ROOT="${HOME}/.pyenv"
if [ -d "${PYENV_ROOT}" ]; then
     export PATH=${PYENV_ROOT}/bin:$PATH
     eval "$(pyenv init -)"
fi
(Omitted)

Install Python 3.7.7

I tried installing Python 3.7.7 again, but this time the installation is complete.

$ pyenv install 3.7.7
python-build: use [email protected] from homebrew
python-build: use readline from homebrew
Downloading Python-3.7.7.tar.xz...
-> https://www.python.org/ftp/python/3.7.7/Python-3.7.7.tar.xz
Installing Python-3.7.7...
python-build: use readline from homebrew
python-build: use zlib from xcode sdk
Installed Python-3.7.7 to /Users/ecru/.pyenv/versions/3.7.7

Check the version of Python installed by pyenv. Then set 3.7.7 to global.

$ pyenv versions
  system
* 2.7.17 (set by /Users/ecru/.pyenv/version)
  3.7.7
$ pyenv global 3.7.7 
$ python -V
Python 3.7.7

Now the error message stating that numpy can't be imported is gone and abc.py can now be run in the terminal.

That's all for the memorandum.