Embedding a kernel and starting a ipython notebook that knows how to connect to it. Kind of a work-around similar to ipython notebook --existing if it existed.

embed_kernel_and_connected_notebook.py

from IPython import embed_kernel

import start_notebook

def main():
    p = start_notebook.main()
    localDict = { 'a':1, 'b':2 }
    embed_kernel()
    p.kill()

if __name__ == '__main__':
    main()

start_notebook.py

import sys
import os
import json
import subprocess

from IPython.zmq import blockingkernelmanager
from IPython.utils.py3compat import str_to_bytes
from IPython.lib.kernel import find_connection_file

def set_session_key_from_connection_file(config, fname):
    with open(fname) as f:
        s = f.read()
        cfg = json.loads(s)
        if 'key' in cfg:
            config.Session.key = str_to_bytes(cfg['key'])

# TODO: this has a few bugs/limitations e.g. can not restart the
# kernel at the moment
def my_kernel_manager(app, pid):
    class Wrapped(blockingkernelmanager.BlockingKernelManager):
        def start_kernel(self, **kwargs):
            cf = find_connection_file(str(pid), profile=app.profile)
            set_session_key_from_connection_file(app.config, cf)
            self.connection_file = cf
            self._launch_args = kwargs.copy()
            
            self.load_connection_file()

    return Wrapped

def start_notebook(pid):
    from IPython.frontend.html.notebook.notebookapp import NotebookApp
    app = NotebookApp.instance()
    app.initialize()

    KernelManagerClass = my_kernel_manager(app, pid)
    sys.modules['__main__'].KernelManagerClass = KernelManagerClass
    app.kernel_manager.kernel_manager_class = '__main__.KernelManagerClass'
    app.start()

def main():
    argsStr = str(os.getpid())

    # imp.load_source only supports .py
    pyOrPycFile = os.path.abspath(__file__)
    pyFile = '{[0]}.py'.format(os.path.splitext(pyOrPycFile))

    toRun = ';'.join([
                    'import imp', 
                    "mod = imp.load_source('mod', r'{}')".format(pyFile),
                    'mod.start_notebook({})'.format(argsStr)
                    ])

    print toRun

    p = subprocess.Popen([sys.executable, '-c', toRun])
    return p

if __name__ == '__main__':
    main()