Python: Get index of dictionary item in list

Question

I have a list li:

[
{name: "Tom", age: 10},
{name: "Mark", age: 5},
{name: "Pam", age: 7}
]

I want to get the index of the item that has a certain name. For example, if I ask for "Tom" it should give me: 0. "Pam" should give me 2.

Solution 1

>>> from operator import itemgetter
>>> map(itemgetter('name'), li).index('Tom')
0
>>> map(itemgetter('name'), li).index('Pam')
2

If you need to look up a lot of these from the same list, creating a dict as done in Satoru.Logic's answer, is going to be a lot more efficent

Solution 2

You may index the dicts by name

people = [ {'name': "Tom", 'age': 10}, {'name': "Mark", 'age': 5} ]
name_indexer = dict((p['name'], i) for i, p in enumerate(people))
name_indexer.get('Tom', -1)

Comments

[Keith]

Any reason you don't just use a dictionary to begin with?

[0xc0de]

+1, I didn't know this. I had assumed that this problem is too trivial to have a library function like itemgetter and always looped over the dict items :D

[Vincent De Smet]

in python3 it seems the map needs to be wrapped in a list to provide the index method