Jupyter magic to handle notebook exceptions

Question

I have a few long-running experiments in my Jupyter Notebooks. Because I don\'t know when they will finish, I add an email function to the last cell of the notebook, so I au

Answer 1

@show0k gave the correct answer to my question (in regards to magic methods). Thanks a lot! :)

That answer inspired me to dig a little deeper and I came across an IPython method that lets you define a custom exception handler for the whole notebook.

I got it to work like this:

from IPython.core.ultratb import AutoFormattedTB

# initialize the formatter for making the tracebacks into strings
itb = AutoFormattedTB(mode = 'Plain', tb_offset = 1)

# this function will be called on exceptions in any cell
def custom_exc(shell, etype, evalue, tb, tb_offset=None):

    # still show the error within the notebook, don't just swallow it
    shell.showtraceback((etype, evalue, tb), tb_offset=tb_offset)

    # grab the traceback and make it into a list of strings
    stb = itb.structured_traceback(etype, evalue, tb)
    sstb = itb.stb2text(stb)

    print (sstb) # <--- this is the variable with the traceback string
    print ("sending mail")
    send_mail_to_myself(sstb)

# this registers a custom exception handler for the whole current notebook
get_ipython().set_custom_exc((Exception,), custom_exc)

So this can be put into a single cell at the top of any notebook and as a result it will do the mailing in case something goes wrong.

Note to self / TODO: make this snippet into a little python module that can be imported into a notebook and activated via line magic.

Be careful though. The documentation contains a warning for this set_custom_exc method: "WARNING: by putting in your own exception handler into IPython’s main execution loop, you run a very good chance of nasty crashes. This facility should only be used if you really know what you are doing."