Apply a function to all keys of a Python dict

Question

I want to transform all the keys of a Python dict.

For example, if the keys are integers, I want to change each key to be the original value multiplied by 100.

What is the most performance-efficient way to achieve this?

The way I am doing it right now is by storing the original keys in a set and deleting those keys, replacing them by new keys - this had a problem that if I had a key=2 and a key=200 in the original key set, there would be collision, which I would have to handle recursively until I find a key with no collision with the original key-set.

Answer 1

You can use a dict comprehension:

>>> d = {1: 'a', 2: 'b', 3: 'c'}
>>> {k*100: v for k, v in d.items()}
{200: 'b', 300: 'c', 100: 'a'}

Replace items() with iteritems() if you're using Python 2.