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@python.org> wrote:
On Tue, 20 Jun 2023 at 02:37, Peter Bona via Python-list
<python-list@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
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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.
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Regards,
=dn
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