[Tutor] Why does print(a_list.sort()) return None?

[Mark Lawrence]

On 29/03/2015 16:25, boB Stepp wrote:
> On Sun, Mar 29, 2015 at 2:53 AM, Alan Gauld <alan.gauld at btinternet.com> wrote:
>> On 29/03/15 07:00, Cameron Simpson wrote:
>>
>>>    print(a_list.sort())
>>>
>>> is printing the result of "a_list.sort()".
>>>
>>> Like most Python functions that operate on something (i.e. .sort, which
>>> sorts the list in place), the .sort method returns None. And that is
>>> printed.
>>
>>
>> But you can use the sorted() function which returns a
>> sorted copy of the list. So replace your print statement
>> with
>>
>> print(sorted(a_list))
>>
>> gets you the display you want. But does not sort the original.
>> So it depends on whether you just want to display it, or
>> actually want to sort it.
>> Use either:
>>
>> a_list.sort()
>> print(a_list)
>>
>> OR
>>
>> print(sorted(a_list))
>
> Thanks for chiming in on this, Alan. I had not noticed that sorted()
> was an available option. I had focused on available list methods.
> While it does not matter if my actual lists do or do not get sorted,
> my intent was to just have a sorted view of the list, so your
> suggestion works better here and uses one less line of code. Thanks!
>
>

The practice of returning None is standard in Python for anything that 
works in place, so as a parallel see also the difference between 
reverse() and reversed()

As for saving a line of code, I'd much rather write three or four lines 
that I can understand at a glance in six months time [or even tomorrow 
:) ] rather than a potentially obtuse one liner.

<groan>
Glad you've got this sorted
</groan>

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence