Merge two dict with same key

[stullis]

By unpacking each dictionary in that manner, you're essentially doing this:

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

In that case, the interpreter is going to:

1. Initialize the dict
   
2. Set key "b" to 2
   
3. Reset key "b" to 3
   

If you reverse the order of x and y, you'll get the opposite result:

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}
z = {**y, **x}
print(z)

Output:
{'b': 2, 'c': 4, 'a': 1}