Example demonstrating usage of Python's "deepmerge" package. Enjoy!

dictmerge-dm.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Merge dictionaries in a smart way using the "deepmerge" package.
# Works with Python2 and Python3.
# See also https://gist.github.com/amotl/cacde4c62b191a649a21dda48c4ac1fd

# https://pypi.org/project/deepmerge/
# pip install deepmerge
from deepmerge import Merger

def merge_dicts(*dicts):
    """
    Utility function for merging nested dictionaries in a smart way.
    """
    merger = Merger([
            (list, ["append"]),
            (dict, ["merge"])
        ],
        ["override"],
        ["override"]
    )
    return merger.merge(*dicts)


def example1():
    """
    A very basic example
    """
    left  = {'hello': 'world'}
    right = {'foo': 'bar'}
    print merge_dicts(left, right)


def example2():
    """
    Merge nested dictionaries
    """
    left  = {'hello': 'world', 'nested': {'key1': 'value1', 'key2': 'value2'}}
    right = {'foo': 'bar',     'nested': {'key1': u'Räuber', 'key2': 'Hotzenplotz'}}
    print merge_dicts(left, right)


def example3():
    """
    Merge nested dictionaries containing lists
    """
    left  = {'hello': 'world', 'nested': {'allowed_ips': ['1.2.3.4/25']}}
    right = {'foo': 'bar',     'nested': {'allowed_ips': ['5.6.7.8/23']}}
    print merge_dicts(left, right)


if __name__ == '__main__':
    example1()
    example2()
    example3()

output.txt

$ ./dictmerge-dm.py
{'foo': 'bar', 'hello': 'world'}
{'foo': 'bar', 'hello': 'world', 'nested': {'key2': 'Hotzenplotz', 'key1': u'R\xe4uber'}}
{'foo': 'bar', 'hello': 'world', 'nested': {'allowed_ips': ['1.2.3.4/25', '5.6.7.8/23']}}