How to update dictionary key based on value?

Question

I have two dictionaries with similar values, but different keys. I'd like to update the second dictionary db with the key value of the first dictionary user.

What would be the optimal way to do that without overcomplicating logic?

For instance, I have the following dictionaries:

user = {'school': ['books', 'pencils', 'sheets', 'notebooks']}
db = {'education': ['books', 'pencils', 'sheets', 'notebooks'],
      'actors': ['student', 'teacher', 'principal']}

user['school'] and db['education'] have the same list value. I just want to update the key value in db with the one found in user. The way I thought the implementation is the following:

def get_key(my_dict, val):
    for key, value in my_dict.items():
        if val == value: 
            return key 
    return None

res = {}
for key, value in db.items():
    if value in user.values():
        key_user = get_key(user, value)
        if key_user:            
            res.update({key_user: value})
    else:
        res.update({key: value})

print(res)

I am implementing this in Python 3.6.6, so as I understand the order of the dictionary entries is kept.

The desired output would be as follows:

{'school': ['books', 'pencils', 'sheets', 'notebooks'],
 'actors': ['student', 'teacher', 'principal']}

Answer 1

As you said the order was important I think the easiest way is to re-create the dictionary, not very efficient for larger datasets though.

We can iterate db to re-create it, the only thing we need to look at is whether to use the key from user or db. If the key exists inside user_values then we can fetch it's index and use that to get key from user_keys, otherwise we use key.

user = {'school': ['books', 'pencils', 'sheets', 'notebooks']}
db = {'education': ['books', 'pencils','sheets','notebooks'],
      'actors': ['student','teacher','principal']}

user_keys = tuple(user.keys())
user_values = tuple(user.values())

new_db = {user_keys[user_values.index(value)] if value in user_values else key: value for key, value in db.items()}

>>> {'school': ['books', 'pencils', 'sheets', 'notebooks'],
     'actors': ['student', 'teacher', 'principal']}