Adding 2 dictionaries python 2 and 3

adding_dictionaries.py

# Python 3.5 >
>>> x = {'a':3, 'b':4, 'c': 7}
>>> y = {'a': 6, 'b': 8, 'd': 9}
>>> z = {**x, **y}
>>> z
{'a': 6, 'b': 8, 'c': 7, 'd': 9}

# Python 2.x

z = dict(x, **y)
z>>>
{'a': 6, 'c': 7, 'b': 8, 'd': 9}

# Python overrides duplicate keys from left to right