从另一个字典列表中按键更新字典列表

Question

I have two lists of dicts:

a = [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}]
b = [{'id': 1, 'name': 'test'}, {'id': 2, 'name': 'test'}, {'id': 3, 'name': 'test'}, {'id': 4, 'name': 'test'}, {'id': 5, 'name': 'test'}]

I need to update the dicts in a with the key 'name' from the dicts of b by key 'id' . Result which I expected:

a = [{'id': 1, 'name': 'test'}, {'id': 2, 'name': 'test'}, {'id': 3, 'name': 'test'}, {'id': 4, 'name': 'test'}]

How can I do it?

Answer 1

You should first create an "index" of the dictionaries in list b , then you can update list a using a list comprehension:

ib = { d["id"]:d for d in b }
a  = [ {**d,**ib.get(d["id"],{})} for d in a ]

Answer 2

It's probably a filter process, get a list of filter scope first and do the filter

a = [{'id': 1}, {'id': 2}, {'id': 3}, {'id': 4}]
b = [{'id': 1, 'name': 'test'}, {'id': 2, 'name': 'test'}, {
    'id': 3, 'name': 'test'}, {'id': 4, 'name': 'test'}, {'id': 5, 'name': 'test'}]
print(list(filter(lambda x: x['id'] in [i['id'] for i in a], b)))

Result:

[{'id': 1, 'name': 'test'}, {'id': 2, 'name': 'test'}, {'id': 3, 'name': 'test'}, {'id': 4, 'name': 'test'}]

Answer 3

Converting a to a set of ids for membership lookups could be a solution as well:

ids = {x["id"] for x in a}

result = [x for x in b if x["id"] in ids]

print(result)
# [{'id': 1, 'name': 'test'}, {'id': 2, 'name': 'test'}, {'id': 3, 'name': 'test'}, {'id': 4, 'name': 'test'}]