How to get the difference between two dictionaries in Python?

Question

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

I have searched and found some addons/packages like datadiff and dictdiff-master, but when I try to import them in Python 2.7, it says that no such modules are defined.

I used a set here:

first_dict = {} second_dict = {}   value = set(second_dict) - set(first_dict) print value 

My output is:

>>> set(['SCD-3547', 'SCD-3456']) 

I am getting only keys, and I need to also get the values.

Answer 1

I think it's better to use the symmetric difference operation of sets to do that Here is the link to the doc.

>>> dict1 = {1:'donkey', 2:'chicken', 3:'dog'} >>> dict2 = {1:'donkey', 2:'chimpansee', 4:'chicken'} >>> set1 = set(dict1.items()) >>> set2 = set(dict2.items()) >>> set1 ^ set2 {(2, 'chimpansee'), (4, 'chicken'), (2, 'chicken'), (3, 'dog')} 

It is symmetric because:

>>> set2 ^ set1 {(2, 'chimpansee'), (4, 'chicken'), (2, 'chicken'), (3, 'dog')} 

This is not the case when using the difference operator.

>>> set1 - set2 {(2, 'chicken'), (3, 'dog')} >>> set2 - set1 {(2, 'chimpansee'), (4, 'chicken')} 

However it may not be a good idea to convert the resulting set to a dictionary because you may lose information:

>>> dict(set1 ^ set2) {2: 'chicken', 3: 'dog', 4: 'chicken'} 

Answer 2

Try the following snippet, using a dictionary comprehension:

value = { k : second_dict[k] for k in set(second_dict) - set(first_dict) } 

In the above code we find the difference of the keys and then rebuild a dict taking the corresponding values.