Update a dict with part of another dict

You could do it like this:

keys = ['key1', 'key2', 'key3']
dict1.update((k, dict2[k]) for k in keys)

There is no built-in function I know of, but this would be a simple 2-liner:

for key in ('key1', 'key2', 'key3'):
    dict1[key] = dict2[key]  # assign dictionary items