How can I write an IPython cell magic command that runs the code in the cell?

Question

I have written a cell magic for a program I am writing where I want to save the cell to a python file, but I would ideally also want to run the code in the cell so I can use them later in the notebook.

Magic Code

# custom_magic.py
from pathlib import Path

from IPython.core.magic import register_cell_magic


@register_cell_magic
def service_cell(project_dir, cell):
    project_dir = Path(project_dir)
    project_dir.mkdir(parents=True, exist_ok=True)

    with open(project_dir / "service.py", "w") as file_handle:
        file_handle.write(cell)

In the notebook:

from custom_magic import service_cell

%%service_cell notebook_service
def echo(msg: str) -> str:
    return msg

echo("hello")

Output:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-5-b1e6d0cc609b> in <module>
----> 1 echo("helo")

NameError: name 'echo' is not defined

Answer 1

You need to add the following at the start and end of your magic method

from IPython import get_ipython
....
get_ipython().run_cell(cell)

your magic should looks like this

# custom_magic.py
from IPython import get_ipython
from pathlib import Path

from IPython.core.magic import register_cell_magic


@register_cell_magic
def service_cell(project_dir, cell):
    project_dir = Path(project_dir)
    project_dir.mkdir(parents=True, exist_ok=True)

    with open(project_dir / "service.py", "w") as file_handle:
        file_handle.write(cell)

    get_ipython().run_cell(cell)