Python min function with a list of objects

Question

How can use the key argument for the min function to compare a list of objects's 1 attribute?

Example

class SpecialNumber:     def __init__(self, i):         self.number = i  li = [SpecialNumber(1), SpecialNumber(3), SpecialNumber(2)] 

Answer 1

http://docs.python.org/library/operator.html#operator.attrgetter

from operator import attrgetter min_num = min(li,key=attrgetter('number')) 

Sample interactive session:

>>> li = [SpecialNumber(1), SpecialNumber(3), SpecialNumber(2)] >>> [i.number for i in li] [1, 3, 2] >>> min_num = min(li,key=attrgetter('number')) >>> print min_num.number 1 

Answer 2

It's:

min(li, key=lambda x: x.number) 

you need a function that accepts a SpecialNumber and returns its element.