How to subtract values from dictionaries

Question

I have two dictionaries in Python:

d1 = {'a': 10, 'b': 9, 'c': 8, 'd': 7} d2 = {'a': 1, 'b': 2, 'c': 3, 'e': 2} 

I want to substract values between dictionaries d1-d2 and get the result:

d3 = {'a': 9, 'b': 7, 'c': 5, 'd': 7 } 

Now I'm using two loops but this solution is not too fast

for x,i in enumerate(d2.keys()):         for y,j in enumerate(d1.keys()): 

Answer 1

I think a very Pythonic way would be using dict comprehension:

d3 = {key: d1[key] - d2.get(key, 0) for key in d1} 

Note that this only works in Python 2.7+ or 3.