# Python >= 3.5:
def merge_dictionaries(a, b):
return {**a, **b}
# else:
def merge_dictionaries(a, b):
c = a.copy() # make a copy of a
c.update(b) # modify keys and values of a with the b ones
return c
a = { 'x': 1, 'y': 2}
b = { 'y': 3, 'z': 4}
print(merge_dictionaries(a, b)) # {'y': 3, 'x': 1, 'z': 4}