pythondictionary

How to merge and sum of two dictionaries in Python?

I have a dictionary below, and I want to add to another dictionary with not necessarily distinct elements and merge its results.

Is there any built-in function for this, or do I need to make my own?

{
  '6d6e7bf221ae24e07ab90bba4452267b05db7824cd3fd1ea94b2c9a8': 6,
  '7c4a462a6ed4a3070b6d78d97c90ac230330603d24a58cafa79caf42': 7,
  '9c37bdc9f4750dd7ee2b558d6c06400c921f4d74aabd02ed5b4ddb38': 9,
  'd3abb28d5776aef6b728920b5d7ff86fa3a71521a06538d2ad59375a': 15,
  '2ca9e1f9cbcd76a5ce1772f9b59995fd32cbcffa8a3b01b5c9c8afc2': 11
}

The number of elements in the dictionary is also unknown.

Where the merge considers two identical keys, the values of these keys should be summed instead of overwritten.

Solution

  • You didn't say how exactly you want to merge, so take your pick:

    x = {'both1': 1, 'both2': 2, 'only_x': 100}
y = {'both1': 10, 'both2': 20, 'only_y': 200}

print {k: x.get(k, 0) + y.get(k, 0) for k in set(x)}
print {k: x.get(k, 0) + y.get(k, 0) for k in set(x) & set(y)}
print {k: x.get(k, 0) + y.get(k, 0) for k in set(x) | set(y)}

    Results:

    {'both2': 22, 'only_x': 100, 'both1': 11}
{'both2': 22, 'both1': 11}
{'only_y': 200, 'both2': 22, 'both1': 11, 'only_x': 100}