Medium ...

lambda-offload.py

import lambdalayer.mymodule
def lambda_handler(event, context)
    mymodule.offloadedcode(event, context)

lambda-path.py

# to be able to reload existing imports
import importlib
# add my pip location
sys.path.insert(0, '/tmp/upload')
# now import the core
import botocore
# reload it
importlib.reload(botocore)
# and now ready to import boto3
import boto3

lambda-pip.py

def install_with_pip(packages):
    """
    Install pip package into /tmp folder
    """
    print(" -- Installing pip packages")
    logfile = open("/tmp/pip-install.log", "wb")
    for package in packages:
        print(" ---- Installing {}".format(package))
        subprocess.check_call([
            sys.executable, '-m', 'pip', 'install',
            '--upgrade', '-t', PKG_DIR, package], stdout=logfile)