I have two lists of dictionaries, lets say:

a = [{'id': 1, 'name': 'a'}]
b = [{'id': 1, 'city': 'b'}]

I want to have a list that merges every dictionary in both lists with the same ID. In this example i expect to have:

a = [{'id': 1, 'name': 'a', 'city': 'b'}]

Is there any cleaner way of doing it other than a for nested into the other?

Thanks

You can keep track of the ids with another dict (or defaultdict to make things simpler). Then update the items in that dict as you iterate. In the end the dict's values will have your list.

from collections import defaultdict
d = defaultdict(dict)a = [{'id': 1, 'name': 'a'}, {'id': 3, 'name': 'a'}]
b = [{'id': 1, 'city': 'b'}, {'id': 2, 'city': 'c'}, {'id': 3, 'city': 'd'}]for item in a + b:d[item['id']].update(item)
list(d.values())# [{'id': 1, 'name': 'a', 'city': 'b'},
#  {'id': 3, 'name': 'a', 'city': 'd'},
#  {'id': 2, 'city': 'c'}]

Note this will overwrite duplicate values other than id — so if you have two with id: 1 and two different cities, you will only get the last city.