System assigns result in invalid syntax

If I have a cell with

flake8_version = !flake8 --version
flake8_version

, then this executes fine.

However, the equivalent Python representation of it from jupytext is:

# %%
flake8_version = !flake8 --version
flake8_version

which is invalid syntax (and not something I could run flake8 on 😄 )

I’m bringing this up because in https://github.com/mwouts/jupytext/issues/781 you commented

magic commands are always commented out by default

but this one wasn’t commented out.

From a quick glance at the source code, it looks like magics are detected using regular expressions - have you considered using IPython’s TransformerManager and then ast-parsing instead? I’m happy to help out with this if you want greater support for magic detection (at least, in Python notebooks)

[MarcoGorelli]

Other than the official does, I don’t have any extra documentation (other than the docstrings in src/black/handle_ipynb_magics.py from https://github.com/psf/black/pull/2357/files )

[MarcoGorelli]

Also, maybe changing this for everyone would cause many diffs on existing notebooks.

Agreed - but you can keep the commented out magics using this approach. You just use TransformerManager to detect where the magics are, then you “extract” the magic using ast.parse, then you comment / uncomment - so the script would still look like the notebook

In https://github.com/psf/black/pull/2357 I replace the magics with randomly generated tokens, but they could just as easily be replaced with commented-out versions of themselves

I’ll put something together to demonstrate when I get a chance