Python sorting - A list of objects

Question

I'd like to use the somelist.sort() method to do this if possible.

I have a list containing objects, all objects have a member variable resultType that is an integer. I'd like to sort the list using this number.

How do I do this?

Thanks!

Answer 1

somelist.sort(key = lambda x: x.resultType) 

Here's another way to do the same thing that you will often see used:

import operator s.sort(key = operator.attrgetter('resultType')) 

You might also want to look at sorted if you haven't seen it already. It doesn't modify the original list - it returns a new sorted list.

Answer 2

Of course, it doesn't have to be a lambda. Any function passed in, such as the below one, will work

def numeric_compare(x, y):    if x > y:       return 1    elif x == y:       return 0    else:  #x < y       return -1  a = [5, 2, 3, 1, 4] a.sort(numeric_compare) 

Source : Python Sorting

So, in your case ...

def object_compare(x, y):    if x.resultType > y.resultType:       return 1    elif x.resultType == y.resultType:       return 0    else:  #x.resultType < y.resultType       return -1  a.sort(object_compare) 

The aforementioned lambda is definitely the most compact way of doing it, but there's also using operator.itemgetter.

import operator #L = [('c', 2), ('d', 1), ('a', 4), ('b', 3)] map(operator.itemgetter(0), L) #['c', 'd', 'a', 'b'] map(operator.itemgetter(1), L) #[2, 1, 4, 3] sorted(L, key=operator.itemgetter(1)) #[('d', 1), ('c', 2), ('b', 3), ('a', 4)] 

So you'd use itemgetter('resultType'). (Assuming getitem is defined.)

sorted(L, key=operator.itemgetter('resultType'))