Order of pytho objects list

[gillest]

• I have a list of objects.
• Each object has a variable named number.
• All objects are in a list

What I would like to achieve in the most efficient manner is to order my objects by their number var.

An example :

Object1
_number=1

Object4
_number=2

Object3
_number=5

ListObj=[Object1,Object3,Object4]

What I want to get is to be able to get my objects in order by their number :
Object1, Object4, Object3

[Glenton]

It might be possible to do it by assigning the special methods that allow <, > and = to be used, and then sorting it. I haven't tried this.

But failing this, what you want to do is use the bisect module (wonderfully efficient):

import bisect
 
class whatever:
    def __init__(self,num):
        self.num=num
    def __repr__(self):
        return "whatever %d"%self.num
 
ob1=whatever(5)
ob2=whatever(3)
ob3=whatever(4)
 
list1=[ob1,ob2,ob3]
 
def mysort(myl):
    ans=[]
    order=[]
    for ob in myl:
        i=bisect.bisect_left(order,ob.num)
        order.insert(i,ob.num)
        ans.insert(i,ob)
    return ans
 
print "original:",list1
list2=mysort(list1)
print "sorted:",list2
 

This prints out

original: [whatever 5, whatever 3, whatever 4]
sorted: [whatever 3, whatever 4, whatever 5]

[gillest]

It would have take a long time to figure it out myself.
Thanks a lot.

[bvdet]

Here's an example of sorting on a key in Python 2.4 and higher:

>>> class Obj(object):
...     def __init__(self, num):
...         self.num = num
...         
>>> objects = [Obj(6), Obj(2), Obj(12), Obj(4)]
>>> objects
[<__main__.Obj object at 0x034C7510>, <__main__.Obj object at 0x034C7410>, <__main__.Obj object at 0x034C7350>, <__main__.Obj object at 0x034C7310>]
>>> [item.num for item in objects]
[6, 2, 12, 4]
>>> objects.sort(key=lambda x: x.num)
>>> objects
[<__main__.Obj object at 0x034C7410>, <__main__.Obj object at 0x034C7310>, <__main__.Obj object at 0x034C7510>, <__main__.Obj object at 0x034C7350>]
>>> [item.num for item in objects]
[2, 4, 6, 12]
>>>