list - simplify code using an inverse dictionary in python

Question

Consider some mapping my_map that defines the order of some keys, and some dictionary my_dict that maps the same keys into some values:

my_map = {'x' : 2, 'y' : 0, 'z' : 1}
my_dict = {'x' : 'foo', 'z' : 'bar', 'y' : 'baz'}

I want to get an ordered list of the values of my_dict using the order defined by my_map. My best approach of getting there is:

inv_map = {v: k for k, v in my_map.items()}
ordered_list = [my_dict[k] for k in [inv_map[d] for d in range(len(my_map))]]

Is there a less clunky way of doing the same?

question from:https://stackoverflow.com/questions/65928121/simplify-code-using-an-inverse-dictionary-in-python

Answer 1

You can actually use sorted very efficiently here using dict.get:

[my_dict[k] for k in sorted(my_map, key=my_map.get)]

In action:

>>> my_map = {'x' : 2, 'y' : 0, 'z' : 1}
>>> my_dict = {'x' : 'foo', 'z' : 'bar', 'y' : 'baz'}
>>> [my_dict[k] for k in sorted(my_map, key=my_map.get)]
['baz', 'bar', 'foo']