A new old Python

You may have noticed something new in yesterday’s scripts: the shebang lines were


I’ve been using Python 3 for quite a while, but it’s been a version installed through Anaconda, not one that came from Apple. The reasons are

  1. Apple didn’t provide a Python 3 until Catalina; and
  2. I didn’t install Catalina on either of my Macs until this past month.

I intend to keep using the Anaconda-installed version as my regular Python because its environment has all the tools I regularly use in my work: NumPy, SciPy, Pandas, and Matplotlib. But the BitBar scripts were a good way to try out Apple’s Python 3; they needed Python 3’s UTF-8 support1 and didn’t need any of those math/science libraries.

While I said above that Apple provides Python 3 in Catalina, that may be stretching the definition of “provide.” If you look in /usr/bin, you’ll find something called python3, but that something may be just a placeholder. If you haven’t installed the Command Line Developer Tools, trying to execute a script via /usr/bin/python3 will get you an error message about an “invalid active developer path.” This happened to me on one of my Macs; presumably, the CLDTs had already been installed on the other Mac and were updated when I switched to Catalina.

If you need to install the CLDTs, this explanation by Flavio Copes of how to do so via the xcode-select command is clear and concise. Once you’ve done so, you can test your new Python 3 by running

/usr/bin/python3 --version

at the command line. You should get Python 3.7.3 as the response. This was the version released over a year ago, which means its remarkably fresh for an Apple-supplied command-line tool.

If you need to install third-party libraries, as I did with the Mechanize and BeautifulSoup libraries used in my library BitBar script, you’ll have to run the Python 3 version of pip like this:

/usr/bin/pip3 install mechanize

You’ll probably get a warning that your version of pip isn’t up to date. As with Python 3 itself, the pip that comes from Apple is over a year old. It’ll still work.

As I said earlier, I don’t expect to be using Apple’s Python 3 in the future, but it’s nice to see that Mac users can use a modern Python without resort to third-party systems like Homebrew or Anaconda.

  1. OK, they didn’t need UTF-8 support, but I did. I’m too old to keep doing the encode/decode dance