[FIXED] Is there any way to sort a python list by length (longest string first?)

Issue

I need to sort my list comprised of variables created through a class by their name (ex. var.name).

I have tried the .sort(key=len, reverse=True) method but it returns this error:

Traceback (most recent call last):
  File "/home/runner/TPF-Tests/main.py", line 92, in <module>
    newvar=shop(1,possibleplace, 70, inventory)
  File "/home/runner/TPF-Tests/main.py", line 64, in shop
    itemlist.sort(key=len, reverse=True)
TypeError: object of type 'item' has no len()

I am a beginner so explanations would be greatly appreciated.

Solution

Your sort key (key=len) doesn't make any sense. You need to sort on the length of the item.name attribute:

mylist.sort(key=lambda x: len(x.name), reverse=True)

For example:

import dataclasses

@dataclasses.dataclass
class item:
    name: str


mylist = [
    item(name='bob'),
    item(name='alice'),
    item(name='mallory'),
    item(name='mallory'),
    item(name='david'),
    item(name='chuck'),
        ]


mylist.sort(key=lambda x: len(x.name))
print(mylist)

Answered By - larsks