Example demonstrating usage of Python3's "dictionary unpacking" feature. Enjoy!

dictmerge-du.py

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

# Merge dictionaries using Python3's "dictionary unpacking" feature.
# However, this does not do smart things like appropriately merging lists.
# See also https://gist.github.com/amotl/88ea2073d6265e115fe4b14e818549b1


def merge_dicts(defaults, user):
    """
    Use dictionary unpacking for merging nested dictionaries,
    a feature available since Python3.5.

    http://treyhunner.com/2016/02/how-to-merge-dictionaries-in-python/
    https://www.python.org/dev/peps/pep-0448/
    """
    context = {**defaults, **user}
    return context


def example1():
    left = {'hello': 'world'}
    right = {'foo': 'bar'}
    print(merge_dicts(left, right))


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


def example3():
    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-du.py
{'hello': 'world', 'foo': 'bar'}
{'hello': 'world', 'nested': {'key1': 'Räuber', 'key2': 'Hotzenplotz'}, 'foo': 'bar'}
{'hello': 'world', 'nested': {'allowed_ips': ['5.6.7.8/23']}, 'foo': 'bar'}