A cautionary tale of why you should use virtual environments in Python.

What are virtual environments?

Why should you care about using them with Python ๐Ÿ?

I'll answer these two questions...

And I'll do so by telling you how I screwed up by not using virtual envs.


A virtual environment is like a sandbox, a safe place.

In a virtual environment, the packages you install don't interact with the packages outside the env.

That's just it.

That's a virtual environment.

So, why would you care about it?

I can explain, and I'll do so by telling you something that happened to me the other day.

(I think it was on Monday..?)

Lately, I have been playing around with the new rich-cli that @willmcgugan published.

It's a neat tool that lets me, for example, print code files to the terminal with syntax highlighting.

Installing it was easy enough:

pip install rich-cli

After installing it, I used it to highlight the syntax of a .py file I had.

I noticed there was an option to customise the syntax highlighting...

So, I picked the theme Dracula and ran it:

rich c:/tmp/richtest.py --theme dracula

Sadly, it didn't work:

That white background and those bright colours are not the Dracula theme.

I opened an issue on the GitHub page, and Will (the maintainer, nice chap) asked me to try to update pygments.

pygments is a Python package that does syntax highlighting, and rich-cli depends on it.

So, I tried updating pygments, and I managed to do so.

I had version 2.8.1 installed, and updated it to 2.11.2.

After updating, I ran the same command:

rich c:/tmp/richtest.py --theme dracula

And it worked!


Why didn't rich-cli install the correct version of pygments?

When I installed rich-cli, I got this message:

โ€œRequirement already satisfied: pygments<3.0.0,>=2.6.0โ€

That's because I already had pygments on my machine (version 2.8.1).

However, turns out that rich-cli needs a more recent version of pygments!

That's why I had to upgrade pygments...

Even though I already had it, because some other package required it...

So, now that I upgraded pygments, did I break other package(s) that were using pygments v2.8.1..?

I have no idea!

I have no idea because I can't even remember what package(s) required pygments!

I may very well have broken something in my system ๐Ÿ˜ข

This is what virtual environments help protect against!

Imagine I had installed rich-cli in a virtual environment.

In doing so, I would have gotten a fresh install of pygments just for rich-cli, and everything would've worked from the get-go!

So that's why you should care about virtual environments!

I hope this thread was helpful to you! If it was, follow me @mathsppblog for more Python ๐Ÿ content!

And FYI, you can find all my threads in blog form here ๐Ÿ‘‰ https://mathspp.com/blog/twitter-threads


  • Virtual environments create sandboxes for your package installations.
  • They help manage interdependencies by removing interactions between packages.
  • rich-cli is awesome and you should install it.

See you around! ๐Ÿ‘‹

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