Updating python dictionary

[John Machin]

On Sep 8, 7:51 am, "andyh... at gmail.com" <andyh... at gmail.com> wrote:
> Hello...
>
> I have a dict of key/values and I want to change the keys in it, based
> on another mapping dictionary. An example follows:
>
> MAPPING_DICT = {
>     'a': 'A',
>     'b': 'B',
>
> }
>
> my_dict = {
>     'a': '1',
>     'b': '2'
>
> }
>
> I want the finished my_dict to look like:
>
> my_dict = {
>     'A': '1',
>     'B': '2'
>
> }
>
> Whereby the keys in the original my_dict have been swapped out for the
> keys mapped in MAPPING_DICT.
>
> Is there a clever way to do this, or should I loop through both,
> essentially creating a brand new dict?
>

Is this homework?

There seems to be an implicit assumption in the answers so far that
your mapping is a 1:1 mapping of all possible input keys.

If it doesn't include all possible input keys, answers will crash with
a KeyError. If there are any many:1 elements in the mapping (for
example, {'a': 'A', 'b': 'A'}), lossage happens. You may wish to code
in some checks for this.