Python (2 and 3) how to merge two dicts

merge_two_dicts.py

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}

def merge_two_dicts_python3():
    z = {**x, **y}
    print(z)  #  {'c': 4, 'a': 1, 'b': 3}

def merge_two_dicts_python2():
    z = dict(x, **y)
    print(z)  #  {'a': 1, 'c': 4, 'b': 3}