Should NoneType be iterable?

[dn]

On 20/06/2023 06.12, Neal Becker via Python-list wrote:
> On Mon, Jun 19, 2023 at 12:42 PM Chris Angelico via Python-list <
> python-list at python.org> wrote:
> 
>> On Tue, 20 Jun 2023 at 02:37, Peter Bona via Python-list
>> <python-list at python.org> wrote:
>>>
>>> Hi
>>>
>>> I am wondering if there has been any discussion why NoneType  is not
>> iterable My feeling is that it should be.
>>> Sometimes I am using API calls which return None.
>>> If there is a return value (which is iterable) I am using a for loop to
>> iterate.
>>>
>>> Now I am getting 'TypeError: 'NoneType' object is not iterable'.
>>>
>>> (Examples are taken from here
>> https://rollbar.com/blog/python-typeerror-nonetype-object-is-not-iterable/
>> )
>>> Example 1:
>>> mylist = None
>>> for x in mylist:
>>>      print(x)  <== will raise TypeError: 'NoneType' object is not iterable
>>> Solution: extra If statement
>>> if mylist is not None:
>>>      for x in mylist:
>>>          print(x)
>>>
>>>
>>> I think Python should handle this case gracefully: if a code would
>> iterate over None: it should not run any step. but proceed the next
>> statement.
>>>
>>> Has this been discussed or proposed?
>>>
>>
>> Try this instead:
>>
>> for x in mylist or ():
>>
>> Now a None list will skip iteration entirely, allowing you to get the
>> effect you want :)
>>
>> ChrisA
>> --
>> https://mail.python.org/mailman/listinfo/python-list
>>
> I prefer iteration of None to be an error, as in my usage it usually
> indicates a mistake that I'd want to catch

Agreed!

A better approach is that the API return (perhaps a tuple of) both 
"status" and "return_value", rather than overloading the latter.

That said, apparently the OP use-case is for when there is no interest 
in status/catch, eg where a 'nothing' answer is THE answer.

-- 
Regards,
=dn