Quickly testing code in a different Python version using pyenv#

Seeing what versions I had already#

1
pyenv versions

This outputs (on my machine):

1
  system
2
  3.7.16
3
  3.8.17

To see all possible versions:

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pyenv install --list

That’s a long list! I grepped it for 3.8:

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pyenv install --list | grep '3.8'

1
  3.8.0
2
  3.8-dev
3
  3.8.1
4
  3.8.2
5
  ...
6
  3.8.14
7
  3.8.15
8
  3.8.16
9
  3.8.17
10
  ...

Installing a specific version#

I installed 3.8.17 like this:

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pyenv install 3.8.17

This took a long time, because it compiled it from scratch.

Using that version via a virtual environment#

I decided to use that version of Python directly. The binary was installed here:

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~/.pyenv/versions/3.8.17/bin/python

I created a temporary virtual environment in /tmp like this:

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~/.pyenv/versions/3.8.17/bin/python -m venv /tmp/py38env

Then installed my current project into that environment like so:

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/tmp/py38env/bin/pip install -e '.[test]'

Now I can run the tests like this:

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/tmp/py38env/bin/pytest