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 — vaultah
– vaultah, Commented May 31, 2015 at 4:38
I'm not working with a dictionary, but I'll see if I can adapt that Q's answer. — LazerSharks
– LazerSharks, Commented May 31, 2015 at 4:41
I see. Both map and list comprehensions are new to me. Great to be introduced! — LazerSharks
– LazerSharks, Commented May 31, 2015 at 4:45

Community · Accepted Answer · 2017-05-23 10:26:52Z

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]

Paulo Mendes · Accepted Answer · 2015-05-31 04:47:55Z

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]

If you're an experienced programmer checking out Python, you'll probably enjoy the book Dive into Python (www.diveintopython.net).

Paul Rooney · Accepted Answer · 2015-05-31 06:38:29Z

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)

3 Answers 3