IPython Notebook - early exit from cell

Question

I'd like to programmatically exit a cell early in IPython Notebook. exit(0), however, kills the kernel.

Whats the proper way to do this? I'd prefer not to split the cell or manually halt execution.

Answer 1

I'm reposting my answer from here because the solution should apply to your question as well. It will...

• not kill the kernel on exit
• not display a full traceback (no traceback for use in IPython shell)
• not force you to entrench code with try/excepts
• work with or without IPython, without changes in code

Just import 'exit' from the code beneath into your jupyter notebook (IPython notebook) and calling 'exit()' should work. It will exit and letting you know that...

 An exception has occurred, use %tb to see the full traceback.

 IpyExit 

---

"""
# ipython_exit.py
Allows exit() to work if script is invoked with IPython without
raising NameError Exception. Keeps kernel alive.

Use: import variable 'exit' in target script with
     'from ipython_exit import exit'    
"""

import sys
from io import StringIO
from IPython import get_ipython


class IpyExit(SystemExit):
    """Exit Exception for IPython.

    Exception temporarily redirects stderr to buffer.
    """
    def __init__(self):
        # print("exiting")  # optionally print some message to stdout, too
        # ... or do other stuff before exit
        sys.stderr = StringIO()

    def __del__(self):
        sys.stderr.close()
        sys.stderr = sys.__stderr__  # restore from backup


def ipy_exit():
    raise IpyExit


if get_ipython():    # ...run with IPython
    exit = ipy_exit  # rebind to custom exit
else:
    exit = exit      # just make exit importable