IPython magic for save & run a cell (optionally in a subprocess)

withsave_magic.py

from IPython.core.magic import register_cell_magic
import subprocess
import argparse
import sys
import os

@register_cell_magic
def withsave(line, cell):
    parser = argparse.ArgumentParser()
    parser.add_argument('fname')
    parser.add_argument('-f', '--force', action='store_true')
    parser.add_argument('-a', '--append', action='store_true')
    parser.add_argument('--subp')
    parser.add_argument('--no-capout', action='store_false', dest='capout')
    args = parser.parse_args(line.split())
    if not args.fname.endswith('.py'):
        args.fname += '.py'
    assert not (args.force and args.append)
    if os.path.exists(args.fname) and not (args.force or args.append):
        raise FileExistsError(args.fname)
    with open(args.fname, 'a' if args.append else 'w') as f:
        f.write(cell)
    if not args.subp:
        get_ipython().run_cell(cell)
    else:
        get_ipython().user_ns[args.subp] = subprocess.run(
            [sys.executable, args.fname],
            capture_output=args.capout
        )