Strange behavior with sort()

[Eduardo A. Bustamante López]

On Thu, Feb 27, 2014 at 07:24:24AM +0100, ast wrote:
> Hello
> 
> box is a list of 3 integer items
> 
> If I write:
> 
>    box.sort()
>    if box == [1, 2, 3]:
> 
> 
> the program works as expected. But if I write:
> 
>    if box.sort() == [1, 2, 3]:
> 
> it doesn't work, the test always fails. Why ?
> 
> Thx
> -- 
> https://mail.python.org/mailman/listinfo/python-list

Because when you call the .sort() method on a list, it does the sort
in-place, instead of returning a sorted copy of the list. Check this:

>>> [2,1,3].sort()
>>> 

The method does not return a value, that's why the direct comparison
fails.

What you might want is to use the sorted() method on the list, like
this:

>>> sorted([2,1,3])
[1, 2, 3]
>>> sorted([2,1,3]) == [1,2,3]
True

-- 
Eduardo Alan Bustamante López