How to get the difference between two dictionaries in Python?

Question

I have two dictionaries. I need to find the difference between the two which should give me both key and value.

I have searched and found some addons/packages like d

Answer 1

A function using the symmetric difference set operator, as mentioned in other answers, which preserves the origins of the values:

def diff_dicts(a, b, missing=KeyError):
    """
    Find keys and values which differ from `a` to `b` as a dict.

    If a value differs from `a` to `b` then the value in the returned dict will
    be: `(a_value, b_value)`. If either is missing then the token from 
    `missing` will be used instead.

    :param a: The from dict
    :param b: The to dict
    :param missing: A token used to indicate the dict did not include this key
    :return: A dict of keys to tuples with the matching value from a and b
    """
    return {
        key: (a.get(key, missing), b.get(key, missing))
        for key in dict(
            set(a.items()) ^ set(b.items())
        ).keys()
    }

Example

print(diff_dicts({'a': 1, 'b': 1}, {'b': 2, 'c': 2}))

# {'c': (, 2), 'a': (1, ), 'b': (1, 2)}

How this works

We use the symmetric difference set operator on the tuples generated from taking items. This generates a set of distinct (key, value) tuples from the two dicts.

We then make a new dict from that to collapse the keys together and iterate over these. These are the only keys that have changed from one dict to the next.

We then compose a new dict using these keys with a tuple of the values from each dict substituting in our missing token when the key isn't present.