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A Python setup that finally works

Vincent Thorne · Posted 29 Jun 2022

My punctual use of Python lead to a rocky situation on my computer: multiple installed versions of Python with some managed by Anaconda, unruly export PATHs and multiple virtual environments. It (kind of) worked when I needed to, but I felt a complete lack of control. In short, my computer was the embodiment of xkcd’s famous comic:

xkcd comic python environment

That was until my colleague Matteo took the time the other day to teach me his own protocol to install and maintain a healthy Python ecosystem. This post will walk the reader through the steps that helped me achieve Python sanity on macOS.

The Steps

These commands are to be run in the terminal. They assume that you have Homebrew installed (which I recommend — some reasons why): install instructions are available here.

Controversial Step 0: if installed, remove Anaconda completely and clean your .zshrc of all export PATHs created by Anaconda or conda. More details on Anaconda’s help page. Not taking a stance for or against Anaconda/conda here, just advising to clean up old layers of Python before laying the sturdy foundations!

  1. Install Python from Homebrew brew install python
  2. Make sure that the export PATH in .zshrc is set to the one prescribed by Homebrew and that there are no other export paths export PATH="/usr/local/opt/python/libexec/bin:$PATH"
  3. Restart the terminal session
  4. Navigate to the directory of the project cd path/to/project
  5. Install virtualenv with pip pip install virtualenv
  6. Create a new virtual environment virtualenv [environment-name]
  7. Activate (source) the new environment source [environment-name]/bin/activate
  8. Install required packages with pip pip install [package]
  9. If necessary later on, upgrade packages pip install [packages] --upgrade
  10. Once done managing the environment, deactivate it deactivate

Spyder setup

Accustomed to RStudio and other statistical IDEs, Spyder is a close enough cousin to ease my transition into Python. A few further steps are necessary to link it with the custom environment created above.

  1. Install spyder-kernels in the virtual environment pip install spyder-kernels
    • Depending on your version of Spyder, it might ask you to install a specific version. Try with the version displayed first pip install spyder-kernels==2.3.0, for example
  2. In Spyder preferences
    1. Go to the Python Interpreter tab and select “Use the following Python interpreter”.
    2. Click on the file icon
    3. In the Finder prompt, navigate to your virtual environment, the bin folder and select the pyhton file.
    4. Click OK and restart Spyder
  3. Check if it works by import [package] a package installed in your virtual environment using the IPython console in Spyder

Important: if you create a new virtual environment, you will have to make sure that it has spyder-kernels installed (step 1) and re-link Spyder to that new environment (step 2).

Updating and sharing your environment

  1. Export a list of packages with their version to a text file pip freeze > requirements.txt
  2. Update the packages listed in requirements.txt pip install --upgrade -r requirements.txt
  3. Send requirements.txt to someone, and they just need to pip install -r requirements.txt to install all the packages

If nothing works

Take a deep breath and ask your knowledgeable friends and colleagues to take a look at your computer and help you figure things out. There is light at the end of the Python tunnel!