如何从词典列表中的特定键中获取唯一值？

Question

Give I have a list with dictionaries and I want to get all unique values from the key first_name from the dictionaries, how do I do that in python?

data = [
{
    "id": 1,
    "first_name": "John"
},
{   "id": 2,
    "first_name": "Mary"
},
{   "id": 3,
    "first_name": "John"
}
]

Answer 1

您可以使用set comprehension ：

first_names = {d["first_name"] for d in data}

Answer 2

>>> set(i["first_name"] for i in data)
{'John', 'Mary'}

if you want a list instead of set you can convert it to list:

>>> list(set(i["first_name"] for i in data))
['John', 'Mary']

Answer 3

You can map the operator itemgetter() to dictionaries in the list:

from operator import itemgetter

iget = itemgetter('first_name')

set(map(iget, data))
# {'Mary', 'John'}