generate list from values of certain field in list of objects

Question

How would I generate a list of values of a certain field of objects in a list?

Given the list of objects:

[ {name: "Joe", group: 1}, {name: "Kirk", group: 2}, {name: "Bob", group: 1}]

I want to generate list of the name field values:

["Joe", "Kirk", "Bob"]

The built-in filter() function seems to come close, but it will return the entire objects themselves.

I'd like a clean, one line solution such as:

filterLikeFunc(function(obj){return obj.name}, mylist)

Sorry, I know that's c syntax.

possible duplicate of [Get a list of values from a list of dictionaries in python](http://stackoverflow.com/questions/25040875/get-a-list-of-values-from-a-list-of-dictionaries-in-python) — vaultah, May 31 '15 at 04:38
I'm not working with a dictionary, but I'll see if I can adapt that Q's answer. — LazerSharks, May 31 '15 at 04:41
I see. Both `map` and `list comprehensions` are new to me. Great to be introduced! — LazerSharks, May 31 '15 at 04:45

score 3 · Answer 1 · edited May 23 '17 at 10:26

Just replace filter built-in function with map built-in function.

And use get function which will not give you key error in the absence of that particular key to get value for name key.

data = [{'name': "Joe", 'group': 1}, {'name': "Kirk", 'group': 2}, {'name': "Bob", 'group': 1}]

print map(lambda x: x.get('name'), data)

In Python 3.x

print(list(map(lambda x: x.get('name'), data)))

Results:

['Joe', 'Kirk', 'Bob']

print [each.get('name') for each in data]

score 1 · Accepted Answer · answered May 31 '15 at 04:47

1

Using a list comprehension approach you get:

objects = [{'group': 1, 'name': 'Joe'}, {'group': 2, 'name': 'Kirk'}, {'group': 1, 'name': 'Bob'}]
names = [i["name"] for i in objects]

answered May 31 '15 at 04:47

Paulo Mendes

If you're an experienced programmer checking out Python, you'll probably enjoy the book Dive into Python (www.diveintopython.net). – Paulo Mendes May 31 '15 at 06:12

Paul Rooney · Answer 3 · 2015-05-31T06:38:29.620

1

Just iterate over your list of dicts and pick out the name value and put them in a list.

x = [ {'name': "Joe", 'group': 1}, {'name': "Kirk", 'group': 2}, {'name': "Bob", 'group': 1}]

y = [y['name'] for y in x]

print(y)

edited May 31 '15 at 06:38

answered May 31 '15 at 04:51

Paul Rooney

3 Answers3